Rumor has it (from an anonymous source on September 15 here) that the OPERA neutrino detector at CERN is seeing a six sigma signal (above the usual rule of thumb standard for "discovery" in physics) of neutrinos traveling at more than the speed of light, which means that they would be tachyons, the name for particles that travel at more than the speed of light. The experiment's main purpose was to detect tau neutrinos. Data on the speed at which neutrinos travel is simply a bonus (although neutrinos speed, correlated with missing energy in the source reaction, in theory, ought to provide some direct constraints on neutrino mass).
Tommaso Dorigo who blogged this rumor, and Lubos, who blogged Dorigo's gossip, like all good physicists, are deeply skeptical of the result on the theory that extraordinary claims require extraordinary proof. This is only the second credible experiment (the other looked at neutrinos leaving a 1987 supernovae, which has many more uncertainties involved, for example, concerning the distance and the nature of the underlying source), ever, in the history of the universe, to see anything that might be a tachyon at statistically significant levels. There are good theoretical reasons to doubt the result, despite the fact that some quantum mechanical formulas like the Feynman photon propogator in QED recognize that there is a slight statistical probability of particles traveling at more than the speed of light at short distances incorporated into the equation that are interpreted by some as evidence of a slight amount of non-locality in space-time.
A delay in publication of the results or a press release is no doubt due to the frantic efforts of CERN scientists to find some other explanation of the results (the fluke could be as simple as a slight mismeasurement of the 732km distance from the neutrino source to the point at which they were detected, or a clock miscalibration in measuring events about 3 milliseconds long, or an underestimate of statistical uncertainty) so that they don't look stupid when someone else discovers one. But, the experimental setup is generally sound and much of the theoretical analysis is relative straight forward since it does not involve the arcane and complex QCD background calculations that go into making sense of the debris of high energy proton-proton collisions, so this is not an easy result to hand wave away.
The most plausible answer would be that the neutrino impacts that look superluminal didn't actually come from the neutrino generating source that was inferred, and instead came from nuclear reactions either in the Sun, or radioactive isotypes in the Earth (perhaps related to the geological activity of volcanos in central Italy dredging up an excess of radioactive isotypes from the center of the Earth aligned with the neutrino beam), or from some unaccounted for man made source like a nearby smoke alarm with a radioactive isotype that is decaying in it. A failure to properly account for these kind of neutrino backgrounds has already been suggested in the direct detection of dark matter experiments showing a positive detection that have been conducted so far.
But, information on the direction in which the debris from the neutrino impact travels, the momentum of that debris, and statistical tests ought to be able to rule out those kinds of neutrino backgrounds very effectively in a series of results numerous enough to provide a six sigma signal.
UPDATE: The comments at Resonaances and post at Dorigo's blog regarding the rumored results have both been taken down.
Monday, September 19, 2011
Thursday, September 15, 2011
Copper Kills Microbes
The hospital of the future may end up looking like a French kitchen. They are famous for their copper clad pots and pans and it turns out that the preference is more than aethetic. Copper surfaces are natural, broad spectrum disinfectants (something that also explains why copper is critical to IUDs). Intensive care units that replaced conventional surfaces with copper clad ones reduced infections by 40%.
Running Coupling Constants In Low Energy Quantum Chromodynamics
The textbook description of quantum chromodynamics (the quantum theory that explains the interaction of quarks and gluons through the strong force), notes that unlike the electromagnetic force, which grows stronger at higher energies (a phenomena known as the running of the coupling constant for electromagnetism), the coupling constant of the strong force grows weaker at higher energies. These observations, together with the running of the coupling constant of the weak force, produces the charts favored by Grand Unified Theory proponents that show the three coupling constants converging on a common strength at very high energies around 15 TeV (the GUT scale).
The mere fact that coupling constants aren't actually constants, but instead run with the energy level of the interaction via Beta functions is itself a major surprise for most people unfamiliar with quantum physics.
But, even the textbook description has a flaw. It turns out, as QCD theorist Marco Frasca noted in his Gauage Connection blog in a recent post on research in the field, that the running coupling constant of the strong force weakens on both the low energy and high energy sides of the strong force scale (of about 216 MeV) where its coupling constant peaks, something that was not previously noted by researchers using perturbative methods to approximate QCD equation solutions numerically, rather than the numerical approximations used in Lattice QCD, which do not contain a linearizing approximation method used in peturbative QCD calculuations.
This would be a pretty trival matter unimportant except to QCD theorists were it not for some key point that it illustrates that pertinent to all GUT theories.
First, perturbative approximations are not an accurate way of inferring beta functions at extreme values, because they are insufficiently non-linear. If a widely assumed curve for the highly non-linear beta function of the QCD coupling constant is quite wrong, why shouldn't the beta function of some other force be a little bit wrong? Why come up with a major new tweak to theoretical physics that proposes all sorts of new particles and interactions to make the running coupling constants converge when all you really have to do tweak an obscure phenomenological beta function for a coupling constant or two at energy scales where the perturbative approximations used to estimate them probably aren't valid anyway? Tweaking beta functions may be a way to save the Standard Model from problems that seem to be present at high energy and require other fixes. Maybe that isn't the right answer, but there are far too few papers being written that probe whether it could be the right answer.
Second, the chart that GUT theorists favor as an empirical and emotional motivation for GUT theories looks a lot less compelling when you have a running coupling constant for the strong force that goes up before it goes down, rather than converging inexorably upon a unified GUT scale convergence point.
The issue also comes to a head when you look at top quark physics. At the sufficiently high energy scales found in top quarks, QCD breaks down. Top quarks decay before the strong force can produce the hadronization and confinement seen in the physics of the other five quarks. At the energy scale of the top quark (each top quark has a rest mass of between 173 GeV and 174 GeV v. a bottom quark with a rest mass of between 4 GeV and 5 GeV), the strong force seemingly ceases to become a meaningful concept at all. How can you talk about the running of the strong force coupling constant at energy levels where the strong force empirically seems to vanish? What if rather than converging to a fixed point, the strong force coupling constant effectively dips all of the way to zero and drops below the weak force and electromagnetic force coupling constant before any of the three have converged? Yet, doesn't the fact that the weak force produces top quark decays before the strong force can hadronize top quarks just what you would predict in that scenario? Maybe the apparent convergence in coupling constants that we observe is really just a product of true convergence of a unified electroweak force and wild overextrapolation of the running of the strong force coupling constant that doesn't actually converge toward the other two coupling constants at all if better modeled?
It may also not be coincidental that the top quark mass is a great departure from the patterns shown by the mass matrix of the other five quarks that do hadronize (it is much larger in mass than expected). One possible source for this discrepency could be that the conventional masses of the hadronizing quarks are deflated relative to binding energy from gluons in the formula used to parse them out of the confined structures in which they appear. If more of the mass of hadronized quarks than conventionally assumed is in the quarks themselves, and less of the mass of hadronized quarks is in the glue (which is absent from estimates of top quark mass), then the top quark mass isn't anomalous after all.
On the other hand, the apparent experimental confirmation of experimental predictions for a ground state glueball mass would suggest that the conventional quark masses can't be too far off, since the theory seems to estimate glueball mass accurately even when quark contributions are absent.
The mere fact that coupling constants aren't actually constants, but instead run with the energy level of the interaction via Beta functions is itself a major surprise for most people unfamiliar with quantum physics.
But, even the textbook description has a flaw. It turns out, as QCD theorist Marco Frasca noted in his Gauage Connection blog in a recent post on research in the field, that the running coupling constant of the strong force weakens on both the low energy and high energy sides of the strong force scale (of about 216 MeV) where its coupling constant peaks, something that was not previously noted by researchers using perturbative methods to approximate QCD equation solutions numerically, rather than the numerical approximations used in Lattice QCD, which do not contain a linearizing approximation method used in peturbative QCD calculuations.
This would be a pretty trival matter unimportant except to QCD theorists were it not for some key point that it illustrates that pertinent to all GUT theories.
First, perturbative approximations are not an accurate way of inferring beta functions at extreme values, because they are insufficiently non-linear. If a widely assumed curve for the highly non-linear beta function of the QCD coupling constant is quite wrong, why shouldn't the beta function of some other force be a little bit wrong? Why come up with a major new tweak to theoretical physics that proposes all sorts of new particles and interactions to make the running coupling constants converge when all you really have to do tweak an obscure phenomenological beta function for a coupling constant or two at energy scales where the perturbative approximations used to estimate them probably aren't valid anyway? Tweaking beta functions may be a way to save the Standard Model from problems that seem to be present at high energy and require other fixes. Maybe that isn't the right answer, but there are far too few papers being written that probe whether it could be the right answer.
Second, the chart that GUT theorists favor as an empirical and emotional motivation for GUT theories looks a lot less compelling when you have a running coupling constant for the strong force that goes up before it goes down, rather than converging inexorably upon a unified GUT scale convergence point.
The issue also comes to a head when you look at top quark physics. At the sufficiently high energy scales found in top quarks, QCD breaks down. Top quarks decay before the strong force can produce the hadronization and confinement seen in the physics of the other five quarks. At the energy scale of the top quark (each top quark has a rest mass of between 173 GeV and 174 GeV v. a bottom quark with a rest mass of between 4 GeV and 5 GeV), the strong force seemingly ceases to become a meaningful concept at all. How can you talk about the running of the strong force coupling constant at energy levels where the strong force empirically seems to vanish? What if rather than converging to a fixed point, the strong force coupling constant effectively dips all of the way to zero and drops below the weak force and electromagnetic force coupling constant before any of the three have converged? Yet, doesn't the fact that the weak force produces top quark decays before the strong force can hadronize top quarks just what you would predict in that scenario? Maybe the apparent convergence in coupling constants that we observe is really just a product of true convergence of a unified electroweak force and wild overextrapolation of the running of the strong force coupling constant that doesn't actually converge toward the other two coupling constants at all if better modeled?
It may also not be coincidental that the top quark mass is a great departure from the patterns shown by the mass matrix of the other five quarks that do hadronize (it is much larger in mass than expected). One possible source for this discrepency could be that the conventional masses of the hadronizing quarks are deflated relative to binding energy from gluons in the formula used to parse them out of the confined structures in which they appear. If more of the mass of hadronized quarks than conventionally assumed is in the quarks themselves, and less of the mass of hadronized quarks is in the glue (which is absent from estimates of top quark mass), then the top quark mass isn't anomalous after all.
On the other hand, the apparent experimental confirmation of experimental predictions for a ground state glueball mass would suggest that the conventional quark masses can't be too far off, since the theory seems to estimate glueball mass accurately even when quark contributions are absent.
Tuesday, September 13, 2011
Future Physics Students Will Have It Easier
One of the things that makes it so tremendously hard to be a graduate level physics student in fundamental modern physics is that there are a vast number of proposed theories, hypothetical particles, and so on, out there, each of which tends to require some absurdly esoteric kind of mathematical understanding. You must learn not just general relativity and the Standard Model, but also their inconsistencies and all of the experiments that rule out or tend to establish deviations from them.
Someday, and I am optimistic that it will come by the time that my grandchildren are physics students advanced enough to learn quantum mechanics and general relativity, we are going to have all of this worked out, we will have a theory of everything, or at least, a few consistent theories that explain everything at the fundamental laws of physics level, even if they are somewhat ugly and not unified in the grand unified theory or theory of everything sense. The puzzles that remain are few, and the progress we have made so far is great. Dark matter is something of a puzzle, but we can describe limitations on its effects quite well from experiment. Dark energy has a perfectly good answer right now (the cosmological constant of general relativity) that we just need to confirm is the only possible correct answer. There may be only one more (or fewer) fundamental particles less to discover. As almost all of the parameters of the Standard Model are finally pencilled in from experimental data, we are finally starting to clue into the connections between the fermion mass matrix, the CKM matrix, the PMNS matrix, and the coupling constants of the three Standard Model forces, parameterizing them much more efficient as we learn their relationships. Unifying general relativity and the Standard Model is rather less of a chore than determining that the Standard Model is complete and accurate and forms some sort of coherent whole, since honestly, there are very few occasions when both have to be brought to bear and the stylized situations where they do can be solved as special cases with ad hoc intuition guided by experiment if need be. It will make more sense, as well, because the lingering questions will be addressed and will fit better into an overall whole.
When this happens, a vast amount of the stuff that a graduate level physics student needs to know these days will become irrelevant. We can't be quite sure which pieces in particular will become irrelevant, but we can be pretty sure that our hapless graduate student will not need to master both compacted ten dimensional space and the discrete mathematics that goes into loop quantum gravity; both knot theory and Klein-Kaluza topologies; both several MOND theories and several dark matter theories. Our hapless graduate student may need to learn one of each, but probably not both.
Similarly, our hapless graduate student will not need to learn the Standard Model, two or three variations on supersymmetry, technicolor, the SM4, and half a dozen other extensions of the Standard Model. Learning the new and improved Standard Model and that math that goes with it once will be good enough.
Likewise, it is extremely likely that any resolution of the current conundrums of the Standard Model will greatly reduce the nineteen or so parameters that the current model involves, with values that change every other physics conference and take a handbook that runs hundreds of pages to determine. There will be highly precise values for half a dozen constants (a bit like the number of the classical Newtonian/Maxwellian model), and everything else will be calculated exactly from them. The necessary fundamental constants will fit on the book flap of the textbook (except that our hapless graduate student probably won't be using a physical paper textbook anymore). All the little boxes where particles and couple constants and equations go will be filled and there will be no room in the margins for meddling and revisions. The detailed properties of every possible composite particle, calculated out to several significant digits from the handful of fundamental constants, with all their excitations, will fit in a few dozens pages of the CRC Handbook of Chemistry and Physics, along with the periodic table, the table of isotypes and long lists of organic and inorganic chemicals with their properties.
Honestly, I think that it is all going to look surprisingly familiar.
I think it is quite a bit more likely that SUSY and a fortiori, String Theory/M-Theory, will be disproven than it is that it will be confirmed in any form. There may or may not be a Higgs boson, and if there is one, there is a good chance that there will be just one Standard Model one (as the Standard Model seems to manage just fine with a single vev value for the Higgs field). There may be a fourth or higher generation fermion, but there is a good chance that there isn't. I expect no new fundamental bosons besides the Higgs. There might be right handed neutrinos, but there is a good chance that there aren't. A suspect that the trick to getting the coupling constants of the Standard Model forces to align is to tweak the equations (or the way that we approximate them numerically) slightly rather than to doube the number of particles in the zoo. Whatever we find to solve the theoretical problem that the as yet undiscovered Higgs boson has presented us with, I very much doubt that the solution will involve technicolor, even walking technicolor. I very much doubt that the theory that we end up with will include more than five dimensions or that it will include any compactified dimensions or branes. There might, or might not, be a graviton in the final theory; I think it is more likely that quantum gravity, if necessary, will arise from the non-point-like architecture of space-time. There might be one layer of particles more fundamental than the ones we know now.
I wouldn't be surprised to see a reformulatization of QCD that is equivalent to or nearly equivalent to the current theory that makes it easier to calculate. I wouldn't be surprised to see a couple of new and profound new theories that address the issues of the non-localities found in modern physics, the arrow of time, and better define the role of the observer in the outcome of physical processes.
I wouldn't be surprised to see dark matter resolved with a newly discovered "warm dark matter" candidate like a sterile neutrino or glueball, nor would I be surprised to see it resolved with refined calculations using the existing theory of general relativity or a somewhat modified theory of general relativity, perhaps flowing naturally from a quantum level adaptation of it.
Footnote: The vacuum expectation value of the Higgs field is 246 GeV. The Higgs boson, if it exists, is more than 114 GeV and probably less than 130ish GeV. Just to be cute, because it is possible, I will make a prediction. If there is a Higgs boson, it will have a mass of exactly one half of the vev of the Higgs field, i.e. 123 GeV/c^2. If I'm right, you heard it here first. If not, my batting average is still at least as good as the ordinary theoretical physicist.
Of course, if the LHC does discover a single Standard Model Higgs of spin zero, 123 GeV, and no electrical charge or color charge, this would go a long way towards putting all of those theoretical physicists out of business be eliminating much of the motivation for them to come up with new theories. The end of LHC's run may not strictly speaking rule out Sting Theory or SUSY or Technicolor, just as we haven't absolutely ruled out magnetic monopoles and proton decay and flavor changing neutral currents to absolute mathematical certainty.
But if the LHC does nothing but discover the Higgs and confirms the Standard Model until its run is complete, without finding another wiff of "new physics," they aren't going to build another bigger and better particle accelerator to replace it any time soon. If an apparently theoretical sound way to set the values of the PMNS matrix and neutrino masses from LHC data about quarks that if confirmed by all experiments to data, even neutrino experiments are going to start to look a little pointless, like paying people to reconfirm the universality of the force of gravity or F=ma at low masses and speeds.
If LHC runs out of "new physics" and finds a single Standard Model Higgs boson, the only games in town are going to be figuring out dark matter, coming up with a way to make sense of cosmological inflation, coming up with ways to reconcile gravity to the rest of the Standard Model, and improving our ability to do QCD and GR equations in less stylized contexts.
There is an urgency in fundamental physics right now because the foundations of physical science are embarassingly broken. But, the current cracks in the edifice, while troubling, are largely cosmetic. None of the other important unsolved problems in science at the moment depend upon breakthoughs by people engaged in fundamental physics. We know enough about how the world works to manage, brute force style with an ugly theory that works.
Someday, and I am optimistic that it will come by the time that my grandchildren are physics students advanced enough to learn quantum mechanics and general relativity, we are going to have all of this worked out, we will have a theory of everything, or at least, a few consistent theories that explain everything at the fundamental laws of physics level, even if they are somewhat ugly and not unified in the grand unified theory or theory of everything sense. The puzzles that remain are few, and the progress we have made so far is great. Dark matter is something of a puzzle, but we can describe limitations on its effects quite well from experiment. Dark energy has a perfectly good answer right now (the cosmological constant of general relativity) that we just need to confirm is the only possible correct answer. There may be only one more (or fewer) fundamental particles less to discover. As almost all of the parameters of the Standard Model are finally pencilled in from experimental data, we are finally starting to clue into the connections between the fermion mass matrix, the CKM matrix, the PMNS matrix, and the coupling constants of the three Standard Model forces, parameterizing them much more efficient as we learn their relationships. Unifying general relativity and the Standard Model is rather less of a chore than determining that the Standard Model is complete and accurate and forms some sort of coherent whole, since honestly, there are very few occasions when both have to be brought to bear and the stylized situations where they do can be solved as special cases with ad hoc intuition guided by experiment if need be. It will make more sense, as well, because the lingering questions will be addressed and will fit better into an overall whole.
When this happens, a vast amount of the stuff that a graduate level physics student needs to know these days will become irrelevant. We can't be quite sure which pieces in particular will become irrelevant, but we can be pretty sure that our hapless graduate student will not need to master both compacted ten dimensional space and the discrete mathematics that goes into loop quantum gravity; both knot theory and Klein-Kaluza topologies; both several MOND theories and several dark matter theories. Our hapless graduate student may need to learn one of each, but probably not both.
Similarly, our hapless graduate student will not need to learn the Standard Model, two or three variations on supersymmetry, technicolor, the SM4, and half a dozen other extensions of the Standard Model. Learning the new and improved Standard Model and that math that goes with it once will be good enough.
Likewise, it is extremely likely that any resolution of the current conundrums of the Standard Model will greatly reduce the nineteen or so parameters that the current model involves, with values that change every other physics conference and take a handbook that runs hundreds of pages to determine. There will be highly precise values for half a dozen constants (a bit like the number of the classical Newtonian/Maxwellian model), and everything else will be calculated exactly from them. The necessary fundamental constants will fit on the book flap of the textbook (except that our hapless graduate student probably won't be using a physical paper textbook anymore). All the little boxes where particles and couple constants and equations go will be filled and there will be no room in the margins for meddling and revisions. The detailed properties of every possible composite particle, calculated out to several significant digits from the handful of fundamental constants, with all their excitations, will fit in a few dozens pages of the CRC Handbook of Chemistry and Physics, along with the periodic table, the table of isotypes and long lists of organic and inorganic chemicals with their properties.
Honestly, I think that it is all going to look surprisingly familiar.
I think it is quite a bit more likely that SUSY and a fortiori, String Theory/M-Theory, will be disproven than it is that it will be confirmed in any form. There may or may not be a Higgs boson, and if there is one, there is a good chance that there will be just one Standard Model one (as the Standard Model seems to manage just fine with a single vev value for the Higgs field). There may be a fourth or higher generation fermion, but there is a good chance that there isn't. I expect no new fundamental bosons besides the Higgs. There might be right handed neutrinos, but there is a good chance that there aren't. A suspect that the trick to getting the coupling constants of the Standard Model forces to align is to tweak the equations (or the way that we approximate them numerically) slightly rather than to doube the number of particles in the zoo. Whatever we find to solve the theoretical problem that the as yet undiscovered Higgs boson has presented us with, I very much doubt that the solution will involve technicolor, even walking technicolor. I very much doubt that the theory that we end up with will include more than five dimensions or that it will include any compactified dimensions or branes. There might, or might not, be a graviton in the final theory; I think it is more likely that quantum gravity, if necessary, will arise from the non-point-like architecture of space-time. There might be one layer of particles more fundamental than the ones we know now.
I wouldn't be surprised to see a reformulatization of QCD that is equivalent to or nearly equivalent to the current theory that makes it easier to calculate. I wouldn't be surprised to see a couple of new and profound new theories that address the issues of the non-localities found in modern physics, the arrow of time, and better define the role of the observer in the outcome of physical processes.
I wouldn't be surprised to see dark matter resolved with a newly discovered "warm dark matter" candidate like a sterile neutrino or glueball, nor would I be surprised to see it resolved with refined calculations using the existing theory of general relativity or a somewhat modified theory of general relativity, perhaps flowing naturally from a quantum level adaptation of it.
Footnote: The vacuum expectation value of the Higgs field is 246 GeV. The Higgs boson, if it exists, is more than 114 GeV and probably less than 130ish GeV. Just to be cute, because it is possible, I will make a prediction. If there is a Higgs boson, it will have a mass of exactly one half of the vev of the Higgs field, i.e. 123 GeV/c^2. If I'm right, you heard it here first. If not, my batting average is still at least as good as the ordinary theoretical physicist.
Of course, if the LHC does discover a single Standard Model Higgs of spin zero, 123 GeV, and no electrical charge or color charge, this would go a long way towards putting all of those theoretical physicists out of business be eliminating much of the motivation for them to come up with new theories. The end of LHC's run may not strictly speaking rule out Sting Theory or SUSY or Technicolor, just as we haven't absolutely ruled out magnetic monopoles and proton decay and flavor changing neutral currents to absolute mathematical certainty.
But if the LHC does nothing but discover the Higgs and confirms the Standard Model until its run is complete, without finding another wiff of "new physics," they aren't going to build another bigger and better particle accelerator to replace it any time soon. If an apparently theoretical sound way to set the values of the PMNS matrix and neutrino masses from LHC data about quarks that if confirmed by all experiments to data, even neutrino experiments are going to start to look a little pointless, like paying people to reconfirm the universality of the force of gravity or F=ma at low masses and speeds.
If LHC runs out of "new physics" and finds a single Standard Model Higgs boson, the only games in town are going to be figuring out dark matter, coming up with a way to make sense of cosmological inflation, coming up with ways to reconcile gravity to the rest of the Standard Model, and improving our ability to do QCD and GR equations in less stylized contexts.
There is an urgency in fundamental physics right now because the foundations of physical science are embarassingly broken. But, the current cracks in the edifice, while troubling, are largely cosmetic. None of the other important unsolved problems in science at the moment depend upon breakthoughs by people engaged in fundamental physics. We know enough about how the world works to manage, brute force style with an ugly theory that works.
More Experiments, No New Physics.
New lower bounds have been set for various forms of beyond the Standard Model physics at LHC at the 95% confidence level based on dijet observations:
Excited quarks q* = 2.07 TeV
Randall-Meade Quantum Black Holes (for n=6) = 3.37 TeV
Axigluon = 2.01 TeV
Color Octet Scalar = 1.71 TeV
There are also new SUSY limits: "squark masses below 1.1 TeV are excluded at 95% CL. Gluino masses below 1.1 TeV are also ruled out at 95% CL for values of the universal scalar mass parameter below 500 GeV."
And, "Lepton flavor violations in charged lepton give good signatures for the new physics. We review recent searches for lepton flavor violation in tau decays at B-factories. In these searches, optimization for background reduction is important to obtain high sensitivity. No evidence for these decays is observed and 90% confidence level upper limits have been set on the branching fractions at the O(10^{-8}) level."
Finally, another weird relationship:
The concept was noted here in 1990 and applied, for example, here to make neutrino mixing predictions.
Thus, it may be that the four parameters each that go into the CKM and PMNS matrixes may really be a single set of four parameters, and if suspicions that mass ratios and related to the CKM and PMNS matrixes, then those four parameters could explain the mass matrixes of the fermions as well (plus a base mass from which all other mass could be derived). See, e.g. here and here, and here.
Excited quarks q* = 2.07 TeV
Randall-Meade Quantum Black Holes (for n=6) = 3.37 TeV
Axigluon = 2.01 TeV
Color Octet Scalar = 1.71 TeV
There are also new SUSY limits: "squark masses below 1.1 TeV are excluded at 95% CL. Gluino masses below 1.1 TeV are also ruled out at 95% CL for values of the universal scalar mass parameter below 500 GeV."
And, "Lepton flavor violations in charged lepton give good signatures for the new physics. We review recent searches for lepton flavor violation in tau decays at B-factories. In these searches, optimization for background reduction is important to obtain high sensitivity. No evidence for these decays is observed and 90% confidence level upper limits have been set on the branching fractions at the O(10^{-8}) level."
Lepton-flavor-violating (LFV) decays of charged leptons are expected to have negligible probability even including neutrino oscillations in the Standard Model (SM). The branching fractions of
τ− → μ−γ including SM+ neutrino oscillations are less than O(10−40).
However, many extensions of SM, such as supersymmetry (SUSY) and large extra dimensions, predict enhanced LFV decays with branching fractions close to the current experimental sensitivity. With certain combinations of new physics parameters, the branching fractions for LFV
τ decays can be as high as
10−7, which is already accessible in high-statistics B-factory experiments. Therefore, an observation of LFV decay will be a clear signature for new physics beyond the SM.
τ leptons are expected to be coupled strongly with new physics and have many
possible LFV decay modes due to their large mass. Therefore,τ leptons are ideal objects to search for the LFV decays. SUSY, which is the most popular candidate among New Physics (NP) models, induces naturally LFV at one-loop through the scalar lepton mixing.
If a typical SUSY mass is larger than∼ 1 TeV, processes via one-loop contributions with SUSY particles are suppressed. When scalar leptons are much heavier than weak scale, LFV occurs via a Higgs-mediated LFV mechanism.
Finally, another weird relationship:
it has been noted that the solar and atmospheric neutrino mixing
angles 12 and 23 measured from neutrino oscillation experiments and the quark mixing angles q12 and q23 reveal a surprising relation
12 + q12 ≃ 23 + q23 ≃ 45◦, (3)
which is satisfied by the experimental results
12 + q12 = 47.4 ± 1.1 +3.3−3.0 ◦ and 23 + q23 =45.2+4.2−2.9 +10.8−7.4 ◦
to within a few percent accuracy [1, 2]. This quark-lepton complementarity(QLC) relation (3) has been interpreted as an evidence for certain quark-lepton symmetry or quark-lepton unification as shown in [6]. In the light of the QLC, it is still experimentally allowed for the neutrino mixing matrix to be composed of a CKM-like matrix and maximal mixing matrices as shown in [7, 8].
In [7], it is shown in the framework of supersymmetric standard model that different combination of the mixing matrix leads to different prediction for the branching ratios of lepton flavor violating decays li → lj, which makes it possible to discriminate the possible compositions. Among possible compositions, in this paper, we consider the following parametrization:
U(PMNS) = R(32) (pi/4) U(†CKM) R(21) (pi/ 4),
(4) where UCKM denotes the CKM mixing matrix. The reason why we consider this particular parametrization for the QLC relation is that it is well compared and has similar merit to the triminimal parametrization so that we can simply examine if the effects of deviations from the TB mixing can be compatible with the QLC relation or not by investigating a few observables presented by simple formulas. The parametrization given by Eq.(4) can be obtained from the grand unification or quark-lepton symmetry as shown in [7].
The concept was noted here in 1990 and applied, for example, here to make neutrino mixing predictions.
Thus, it may be that the four parameters each that go into the CKM and PMNS matrixes may really be a single set of four parameters, and if suspicions that mass ratios and related to the CKM and PMNS matrixes, then those four parameters could explain the mass matrixes of the fermions as well (plus a base mass from which all other mass could be derived). See, e.g. here and here, and here.
Newtonian galactic dynamics as an alternative to dark matter?
This article suggests that hot gas dynamics in complex galactic systems in circumstances where general relativity is effectively approximated by Newtonian gravity may produce effects conventionally explained as dark matter or MOND. I'm skeptical, but it probably deserves a look.
Genetic Substrates In Afro-Asiatic Language Speaking Populations
What follows is a collection of factual observations about the population genetics of Afro-Asiatic language family speakers and populations in some ways related to or distinct from them, and some analysis of those facts. It is a work in progress towards making sense of the hard to fit together puzzle pieces of a complex linguistic family's origins.
There are four Y-DNA haplogroups associated with Afro-Asiatic language speaking populations to some extent or another: E1b1b, the exclusive distinctive Y-DNA haplogroup in Berbers which is found is all but Chadic speakers, R1b-V88 associated with Chadic speakers, J associated most strongly with Semitic speakers, and T associated most strongly with Cushitic, Ethiosemitic and Coptic speakers (including Arabic or Berber language speakers of Egyptian descent).
R1b-V88, J and T, when found in Africa, are back migrations. E1b1b is East African (probably Ethiopian) in origin. With a few exceptions, the combined set of Afro-Asiatic Y-DNA haplogroups account for 70% or more of all sampled Afro-Asiatic populations available to the public, and in some cases that percentage exceeds 90%. But, apart from one modest sized sample of Algerian Arabs, there are also Y-DNA haplogroups in the population beyond those associated with Afro-Asiatic populations.
The overall Afro-Asiatic percentage and the nature of the "background" haplogroups varies by region. In the Levant and Egypt, the largest components of the background tends to be Y-DNA haplogroups G and I (suggestive of Anatolian and Caucasian influences). In Mesopotamia and Arabia, the largest component of the background tends to be Y-DNA haplogroup R1a (suggestive of West Asian influences). In Chadic, Berber and North African Arab populations, the largest component of the background tends to be Y-DNA haplogroup E1b1a (suggestive of West African influences). In East Africa (Ethiosemtic, Cushitic and Omotoic and well as some Sudanese populations), the largest component of the background tends to be Y-DNA haplogroups A and B (suggestive of a Khoisan language macrofamily and Pygmy macrofamily affinity). The background for Jews tends to reflect their ancestral geographic neighbors (e.g. Europeans).
Of these backgrounds, I find the East African background, which I would have naively expected to be E1b1a dominated, to be the most interesting. It suggests that haplogroups A and B were predominant in the region (and locally, it is mostly heavily one or the other of them), prior to the later in time expansion of E1b1b, and provides inferential evidence against a hypothesis that Niger-Congo languages or something fairly closely related may have been spoken in East Africa before the rise of Afro-Asiatic languages.
The two populations of Afro-Asiatic population descent showing the largest backgrounds in Africa and the Middle East are East Africans and Jews, each of which have some communities background percentages as high as 40%-50% of the male population sampled. The large background in East Africa could either indicate the petering out of a wave of advance at the periphery in the face of indigenous resistance, or could indicate the limited ability of E1b1b bearers to surmount already well established local competition in their expansion.
The "signal" in the case of Berbers and Chadic populations is strongly form a single Y-DNA haplogroup (E1b1b and R1b-V88 respectively), but in other populations the Afro-Asiatic markers tends to include some mix of haplogroups. Isolated traces of haplogroup J in Berbers is probably attributable to Arab/Bedouin influences. Haplogroup T, for example, while strongly associated with Afro-Asiatic populations in Africa, is almost never the exclusive Y-DNA marker associated with an Afro-Asiatic population that is found in a sample.
The great distinction in both signal and background between the populations on either side of the Gate of Tears at the Southern extent of the Red Sea suggests that the back migrations of Eurasian haplogroups that are associated with Afro-Asiatic populations took place via the Levant and across the Sinai or along its coast (and from there either down the Egyptian coast of the Red Sea or via the Nile to its source or parallel to the Nile during wet Sahara periods, or along the North African coast), and to a lesser extent via contacts between North Africans and Iberia (and to a less extent the entire Southern European coast during classical times), rather than at the Gate of Tears location often associated with the Out of Africa event.
It is a bit hard to tell if the Somolian Y-DNA haplogroup T population has coastal origins, or if it followed the Blue Nile to its source and then made the short hop from the Blue Nile basin to the Indian Ocean drainage basin. Y-DNA haplogroup T could have gone Southeast to Egypt and Northeast to Europe, while Y-DNA haplogroup L could have split from T and K somewhere in the Fertile Crescent and migrated to Pakistan as part of the Harappan population (along with R2 which also has a well defined Indus River Basin distribution).
The relatively clear delineation between Chadic populations and their neighbors with religious and food production similarities (e.g. with the Fulani and Saharan subgroups of Nilo-Saharans), relative to other families of Afro-Asiatic populations, suggests to me that they are quite young among the main linguistic subgroups of Afro-Asiatic. Ethiosemitic is also known in an approximately Bronze Age time frame to have emerged from a single language of Southwest Asian origins upon a Cushitic/Coptic substrate. Arabic's expansion likewise, took place in historic times in the 1st and 2nd millenia.
We know that Semitic was thriving as the language of the Akkadian and subsequent Assyrian empires in the Bronze Age. We know from recovered and dated artifacts that there was trade from Arabia (probably via Yemen) as far as Zanzibar as far back as at least 2,400 BCE, that the Indian Ocean trade was operating in the 1st century CE connecting Zanzibar, Arabia and South Asia, at least, that the African groups that fused with Austronesians to settle Madagascar were very likely East African Bantus, and that Zanzibar probably acquired iron age Bantu settlement around the 9th century CE. An island off Kenya that was part of the same trading system as Zanzibar is called Lemu (a name which is suggestive of the legendary homeland of the Tamils called Lemuria and may have been named in the same place naming tradition although the sleepy island is an unlikely homeland for anyone). We know that there was a healthy Atlantic maritime trade network in the pre-Celtic megalithic culture starting around the 4th century BCE and until roughly Bronze Age collapse ca. 1200 BCE, as a proof of existence of technology at that time.
The subhaplogroup structure found in E1b1b suggests that this haplogroup has its origins in Ethiopia, where diversity is greatest and closer to the origins of E1b1a and E2, while Berbers are at the periphery.
Berbers are also at the tail end of expansions of mtDNA M1 and U6, which are probably back migrations to Africa despite the fact that they are largely confined to Afro-Asiatic Africa. The mtDNA haplogroup L3* found in Berbers is old, rather than of recent origin in the Transafrican slave trade. About 10%-20% of Berber mtDNA is Subsaharan African in origin, while about 60% involves haplogroups usually associated with Caucasians of European and Middle Eastern origins. The mtDNA pool of both Chadic, Cushitic and Omotic populations is composed to a great extent of mtDNA haplogroups L2 and L3 similarly to their neighbors who speak different languages, suggesting a male dominated arrival pattern of Afro-Asiatic language expansion.
Ancient DNA shows genetic continuity between Berbers and North African populations from 12,000 years ago.
The notion of Omotic is an admixture of Nilo-Saharan and Cushitic influences is plausible and could explain its out group status.
Also, genetically, some Nilo-Saharan populations look more like Afro-Asiatic populations than they do like Niger-Congo or prototypical Nilo-Saharan populations.
There are several key historical transitions that it would be nice to be able to link to linguistic expansions in Africa.
The arrival of Fertile Crescent food production technologies in Egypt and Egyptian domestication of the donkey (one or two thousand years after they were developed, ca. 6000-7000 BCE). The arrival of certain Fertile Crescent herd animals in North Africa, East Africa and the Sahel (a few centuries later). The Afro-Asiatic linguistic groups seem primarily connected to the Fertile Crescent rather than to the Sahel agricultural complex. Egyptian trade routes which can be corroborated to some extent not only by historical accounts but by the products that they exported to Egypt may have extended as far as modern Uganda and surely reached Ethiopia, at least.
The expansion of Sahel agriculture (by some accounts contemporaneous with the Fertile Crescent agricultural complex and by some accounts several thousand years later, perhaps as late as 4000 BCE). The domestication of select East African domesticates (e.g. coffee and certain Ethiopian grains). There is an argument that Sahel agriculture only came into its own when East African domesticates and Sahel domesticates merged.
It is probably fair to associate the expansion of E1b1a and the Niger-Congo languages and mtDNA haplogroup L2 with the development of Sahel agriculture, and to associate the later Bantu expansion starting 3,000 BCE with the development of tropical agriculture (with some crops of Austronesian sources) and Bantu iron metallurgy.
The proto-Nilo-Saharans, the proto-Chadic peoples, and the proto-Berbers all appear to have been nomadic pastoral cultures. The transition of the Sahara from its last wet phase in the Holocene when Lake Chad was very large to the current arid phase, was probably formative for at least some of them. There was a major regionally disruptive drought around 2000 BCE and another not quite as bad accompanied by other disasters like volcanos as well around 1200 BCE.
The origin stories of the Semitic peoples are also nomadic pastoral, a tradition that may have persisted at least prior to the Akkadian empire, Assyrian empire, and Phoenicians. Biblical accounts of the early Hebrews portray them as an initially nomadic pastoral culture that starts to transition to agriculture as they settled into the Levant after their exile in Egypt (an event that is suggestive, at least, of having some connection with the Hyskos era and the monotheistic Pharaoh of Egypt, although much of Genesis draws on Mesopotamian legends, something not necessarily inconsistent with the Hyskos).
The Coptic historical record is the oldest in existence apart from the Sumerian one, dating to about 3000 BCE, and is corroborated by the Sumerian historical record which is slightly earlier, ca. 3500 BCE.
The Coptic Egyptian record is less than clear about the origins of the Berbers, Cushitic, Omotic, Chadic and Semitic peoples on their fringes, and archaeology helps only a little to fill the gap.
The Afro-Asiatic languages have considerable time depth relative to the Indo-European and at least some Asian and Altaic language family expansions. They were preceded in Mesopotamia by Sumerian, which was also very likely the source for the Harappan civilization in modern day Pakistan at about the same time as the Egyptian civilization, although the linguistic affinity of Harappan is highly disputed.
The Afro-Asiatic language families do not show a clear linear family tree relationship to each other; almost every combination of groupings has been suggested by legitimate professional linguists. The Northern tier of Afro-Asiatic languages (Berber, Coptic and Semitic) are non-tonal. Cushitic and Omotic and Chadic do have grammatical tone. This suggests either substrate influences or areal influences.
My intuition is that Afro-Asiatic languages either arise from a proto-Afro-Asiatic language in and around Jericho that spread to Egypt and from Egypt to the other Afro-Asiatic language families, or that it radiates from Egypt in all directions. Thus, I am ambivalent about the direction of the Semitic-Coptic link. The close connection to the earliest food production centers makes a Levantine origin for Afro-Asiatic attractive, but the early adoption of a written language could have given Coptic and edge and could have been an indigenous fishing population language (as fishing populations were the most culturally advanced societies prior to food production technologies). The lack of a monolithic Y-DNA or mtDNA signature suggests that some of the transitions were predominantly cultural transfers while others were demic.
My intuition is that the Berber E1b1b/mtDNA L3* combination, quite possibly as a unit, arrived in North Africa in the pre-Neolithic times (ca. 12,000 BCE) as a hunter-gather population that in some way made a leap that set it apart from prior cultures in the area and caused it to expand from East Africa before the Afro-Asiatic languages arose, and Berbers then transitioned culturally with very little genetic impact to a nomadic pastoralist society with an Afro-Asiatic language derived from Coptic when herd animals arrived from Egypt ca. 5000-6000 BCE. The mtDNA M1/U6 could be fellow travellers with Y-DNA E1b1b or with T that would have also been a back migration.
My intuition is that Cushitic is the product of the expansion of Coptic society towards the source of the Blue Nile at about the time of agricultural technology and trade influences from Egypt, with quite heavy substrate influence, and that Omotic is basically Cushitic under heavy Nilo-Saharan influence on the border of the two language groups.
My intuition is that Y-DNA J in Africa is a late in time influence (Ethiosemitic and later) driven by Semitic peoples, and that Y-DNA haplogroup T is an ancient one (quite possibly the most ancient Afro-Asiatic marker given its presence in both the Levant and Europe and Egypt and Cushitic areas). Of course, J is almost surely in Southwest Asia much earlier. I suspect that J1 is originally more closely associated with Semitic languages (possibly in connection with of after Y-DNA T), but that J2 introgresses to some extent into the mix. A specific time depth of J in Southwest Asia and West Asia is for another day.
R1b-V88 should probably be similar in time to the expansion of R1b elsewhere to break off from it basally, but if it was present in a refugium in the Dead Sea area, for example, it could have formed a basis for the Chadic peoples later in time - I suspect that the Chadic peoples could have origins in the early period of Egyptian written history and went almost unmentioned or could have origins shortly before Egyptian written history. There is some indication from their distribution that Chadic peoples may have arrived via oasis hopping in a wetter Sahara Holocene period parallel to but West of the Nile, rather than down the Nile, although tracing the White Nile to its source and then hopping into the Chad basin would also make sense.
Note: This post is light on links and actual data, because I want to get my analysis down and my data are in my favorites bar and a hand written journal, neither of which is prone to memory lapses.
There are four Y-DNA haplogroups associated with Afro-Asiatic language speaking populations to some extent or another: E1b1b, the exclusive distinctive Y-DNA haplogroup in Berbers which is found is all but Chadic speakers, R1b-V88 associated with Chadic speakers, J associated most strongly with Semitic speakers, and T associated most strongly with Cushitic, Ethiosemitic and Coptic speakers (including Arabic or Berber language speakers of Egyptian descent).
R1b-V88, J and T, when found in Africa, are back migrations. E1b1b is East African (probably Ethiopian) in origin. With a few exceptions, the combined set of Afro-Asiatic Y-DNA haplogroups account for 70% or more of all sampled Afro-Asiatic populations available to the public, and in some cases that percentage exceeds 90%. But, apart from one modest sized sample of Algerian Arabs, there are also Y-DNA haplogroups in the population beyond those associated with Afro-Asiatic populations.
The overall Afro-Asiatic percentage and the nature of the "background" haplogroups varies by region. In the Levant and Egypt, the largest components of the background tends to be Y-DNA haplogroups G and I (suggestive of Anatolian and Caucasian influences). In Mesopotamia and Arabia, the largest component of the background tends to be Y-DNA haplogroup R1a (suggestive of West Asian influences). In Chadic, Berber and North African Arab populations, the largest component of the background tends to be Y-DNA haplogroup E1b1a (suggestive of West African influences). In East Africa (Ethiosemtic, Cushitic and Omotoic and well as some Sudanese populations), the largest component of the background tends to be Y-DNA haplogroups A and B (suggestive of a Khoisan language macrofamily and Pygmy macrofamily affinity). The background for Jews tends to reflect their ancestral geographic neighbors (e.g. Europeans).
Of these backgrounds, I find the East African background, which I would have naively expected to be E1b1a dominated, to be the most interesting. It suggests that haplogroups A and B were predominant in the region (and locally, it is mostly heavily one or the other of them), prior to the later in time expansion of E1b1b, and provides inferential evidence against a hypothesis that Niger-Congo languages or something fairly closely related may have been spoken in East Africa before the rise of Afro-Asiatic languages.
The two populations of Afro-Asiatic population descent showing the largest backgrounds in Africa and the Middle East are East Africans and Jews, each of which have some communities background percentages as high as 40%-50% of the male population sampled. The large background in East Africa could either indicate the petering out of a wave of advance at the periphery in the face of indigenous resistance, or could indicate the limited ability of E1b1b bearers to surmount already well established local competition in their expansion.
The "signal" in the case of Berbers and Chadic populations is strongly form a single Y-DNA haplogroup (E1b1b and R1b-V88 respectively), but in other populations the Afro-Asiatic markers tends to include some mix of haplogroups. Isolated traces of haplogroup J in Berbers is probably attributable to Arab/Bedouin influences. Haplogroup T, for example, while strongly associated with Afro-Asiatic populations in Africa, is almost never the exclusive Y-DNA marker associated with an Afro-Asiatic population that is found in a sample.
The great distinction in both signal and background between the populations on either side of the Gate of Tears at the Southern extent of the Red Sea suggests that the back migrations of Eurasian haplogroups that are associated with Afro-Asiatic populations took place via the Levant and across the Sinai or along its coast (and from there either down the Egyptian coast of the Red Sea or via the Nile to its source or parallel to the Nile during wet Sahara periods, or along the North African coast), and to a lesser extent via contacts between North Africans and Iberia (and to a less extent the entire Southern European coast during classical times), rather than at the Gate of Tears location often associated with the Out of Africa event.
It is a bit hard to tell if the Somolian Y-DNA haplogroup T population has coastal origins, or if it followed the Blue Nile to its source and then made the short hop from the Blue Nile basin to the Indian Ocean drainage basin. Y-DNA haplogroup T could have gone Southeast to Egypt and Northeast to Europe, while Y-DNA haplogroup L could have split from T and K somewhere in the Fertile Crescent and migrated to Pakistan as part of the Harappan population (along with R2 which also has a well defined Indus River Basin distribution).
The relatively clear delineation between Chadic populations and their neighbors with religious and food production similarities (e.g. with the Fulani and Saharan subgroups of Nilo-Saharans), relative to other families of Afro-Asiatic populations, suggests to me that they are quite young among the main linguistic subgroups of Afro-Asiatic. Ethiosemitic is also known in an approximately Bronze Age time frame to have emerged from a single language of Southwest Asian origins upon a Cushitic/Coptic substrate. Arabic's expansion likewise, took place in historic times in the 1st and 2nd millenia.
We know that Semitic was thriving as the language of the Akkadian and subsequent Assyrian empires in the Bronze Age. We know from recovered and dated artifacts that there was trade from Arabia (probably via Yemen) as far as Zanzibar as far back as at least 2,400 BCE, that the Indian Ocean trade was operating in the 1st century CE connecting Zanzibar, Arabia and South Asia, at least, that the African groups that fused with Austronesians to settle Madagascar were very likely East African Bantus, and that Zanzibar probably acquired iron age Bantu settlement around the 9th century CE. An island off Kenya that was part of the same trading system as Zanzibar is called Lemu (a name which is suggestive of the legendary homeland of the Tamils called Lemuria and may have been named in the same place naming tradition although the sleepy island is an unlikely homeland for anyone). We know that there was a healthy Atlantic maritime trade network in the pre-Celtic megalithic culture starting around the 4th century BCE and until roughly Bronze Age collapse ca. 1200 BCE, as a proof of existence of technology at that time.
The subhaplogroup structure found in E1b1b suggests that this haplogroup has its origins in Ethiopia, where diversity is greatest and closer to the origins of E1b1a and E2, while Berbers are at the periphery.
Berbers are also at the tail end of expansions of mtDNA M1 and U6, which are probably back migrations to Africa despite the fact that they are largely confined to Afro-Asiatic Africa. The mtDNA haplogroup L3* found in Berbers is old, rather than of recent origin in the Transafrican slave trade. About 10%-20% of Berber mtDNA is Subsaharan African in origin, while about 60% involves haplogroups usually associated with Caucasians of European and Middle Eastern origins. The mtDNA pool of both Chadic, Cushitic and Omotic populations is composed to a great extent of mtDNA haplogroups L2 and L3 similarly to their neighbors who speak different languages, suggesting a male dominated arrival pattern of Afro-Asiatic language expansion.
Ancient DNA shows genetic continuity between Berbers and North African populations from 12,000 years ago.
The notion of Omotic is an admixture of Nilo-Saharan and Cushitic influences is plausible and could explain its out group status.
Also, genetically, some Nilo-Saharan populations look more like Afro-Asiatic populations than they do like Niger-Congo or prototypical Nilo-Saharan populations.
There are several key historical transitions that it would be nice to be able to link to linguistic expansions in Africa.
The arrival of Fertile Crescent food production technologies in Egypt and Egyptian domestication of the donkey (one or two thousand years after they were developed, ca. 6000-7000 BCE). The arrival of certain Fertile Crescent herd animals in North Africa, East Africa and the Sahel (a few centuries later). The Afro-Asiatic linguistic groups seem primarily connected to the Fertile Crescent rather than to the Sahel agricultural complex. Egyptian trade routes which can be corroborated to some extent not only by historical accounts but by the products that they exported to Egypt may have extended as far as modern Uganda and surely reached Ethiopia, at least.
The expansion of Sahel agriculture (by some accounts contemporaneous with the Fertile Crescent agricultural complex and by some accounts several thousand years later, perhaps as late as 4000 BCE). The domestication of select East African domesticates (e.g. coffee and certain Ethiopian grains). There is an argument that Sahel agriculture only came into its own when East African domesticates and Sahel domesticates merged.
It is probably fair to associate the expansion of E1b1a and the Niger-Congo languages and mtDNA haplogroup L2 with the development of Sahel agriculture, and to associate the later Bantu expansion starting 3,000 BCE with the development of tropical agriculture (with some crops of Austronesian sources) and Bantu iron metallurgy.
The proto-Nilo-Saharans, the proto-Chadic peoples, and the proto-Berbers all appear to have been nomadic pastoral cultures. The transition of the Sahara from its last wet phase in the Holocene when Lake Chad was very large to the current arid phase, was probably formative for at least some of them. There was a major regionally disruptive drought around 2000 BCE and another not quite as bad accompanied by other disasters like volcanos as well around 1200 BCE.
The origin stories of the Semitic peoples are also nomadic pastoral, a tradition that may have persisted at least prior to the Akkadian empire, Assyrian empire, and Phoenicians. Biblical accounts of the early Hebrews portray them as an initially nomadic pastoral culture that starts to transition to agriculture as they settled into the Levant after their exile in Egypt (an event that is suggestive, at least, of having some connection with the Hyskos era and the monotheistic Pharaoh of Egypt, although much of Genesis draws on Mesopotamian legends, something not necessarily inconsistent with the Hyskos).
The Coptic historical record is the oldest in existence apart from the Sumerian one, dating to about 3000 BCE, and is corroborated by the Sumerian historical record which is slightly earlier, ca. 3500 BCE.
The Coptic Egyptian record is less than clear about the origins of the Berbers, Cushitic, Omotic, Chadic and Semitic peoples on their fringes, and archaeology helps only a little to fill the gap.
The Afro-Asiatic languages have considerable time depth relative to the Indo-European and at least some Asian and Altaic language family expansions. They were preceded in Mesopotamia by Sumerian, which was also very likely the source for the Harappan civilization in modern day Pakistan at about the same time as the Egyptian civilization, although the linguistic affinity of Harappan is highly disputed.
The Afro-Asiatic language families do not show a clear linear family tree relationship to each other; almost every combination of groupings has been suggested by legitimate professional linguists. The Northern tier of Afro-Asiatic languages (Berber, Coptic and Semitic) are non-tonal. Cushitic and Omotic and Chadic do have grammatical tone. This suggests either substrate influences or areal influences.
My intuition is that Afro-Asiatic languages either arise from a proto-Afro-Asiatic language in and around Jericho that spread to Egypt and from Egypt to the other Afro-Asiatic language families, or that it radiates from Egypt in all directions. Thus, I am ambivalent about the direction of the Semitic-Coptic link. The close connection to the earliest food production centers makes a Levantine origin for Afro-Asiatic attractive, but the early adoption of a written language could have given Coptic and edge and could have been an indigenous fishing population language (as fishing populations were the most culturally advanced societies prior to food production technologies). The lack of a monolithic Y-DNA or mtDNA signature suggests that some of the transitions were predominantly cultural transfers while others were demic.
My intuition is that the Berber E1b1b/mtDNA L3* combination, quite possibly as a unit, arrived in North Africa in the pre-Neolithic times (ca. 12,000 BCE) as a hunter-gather population that in some way made a leap that set it apart from prior cultures in the area and caused it to expand from East Africa before the Afro-Asiatic languages arose, and Berbers then transitioned culturally with very little genetic impact to a nomadic pastoralist society with an Afro-Asiatic language derived from Coptic when herd animals arrived from Egypt ca. 5000-6000 BCE. The mtDNA M1/U6 could be fellow travellers with Y-DNA E1b1b or with T that would have also been a back migration.
My intuition is that Cushitic is the product of the expansion of Coptic society towards the source of the Blue Nile at about the time of agricultural technology and trade influences from Egypt, with quite heavy substrate influence, and that Omotic is basically Cushitic under heavy Nilo-Saharan influence on the border of the two language groups.
My intuition is that Y-DNA J in Africa is a late in time influence (Ethiosemitic and later) driven by Semitic peoples, and that Y-DNA haplogroup T is an ancient one (quite possibly the most ancient Afro-Asiatic marker given its presence in both the Levant and Europe and Egypt and Cushitic areas). Of course, J is almost surely in Southwest Asia much earlier. I suspect that J1 is originally more closely associated with Semitic languages (possibly in connection with of after Y-DNA T), but that J2 introgresses to some extent into the mix. A specific time depth of J in Southwest Asia and West Asia is for another day.
R1b-V88 should probably be similar in time to the expansion of R1b elsewhere to break off from it basally, but if it was present in a refugium in the Dead Sea area, for example, it could have formed a basis for the Chadic peoples later in time - I suspect that the Chadic peoples could have origins in the early period of Egyptian written history and went almost unmentioned or could have origins shortly before Egyptian written history. There is some indication from their distribution that Chadic peoples may have arrived via oasis hopping in a wetter Sahara Holocene period parallel to but West of the Nile, rather than down the Nile, although tracing the White Nile to its source and then hopping into the Chad basin would also make sense.
Note: This post is light on links and actual data, because I want to get my analysis down and my data are in my favorites bar and a hand written journal, neither of which is prone to memory lapses.
Jiao-Lin Xu Asks The Right Questions
Jiao-Lin Xu, a physicist at the University of Georgia in Athens, Georgia (in the United States), is doing some great work asking and answering the big question of how to determine the masses and quantum numbers of the quarks and hadrons of the Standard Model with phenomenological formulas that seek to illuminate the deeper workings of the Standard Model and reduce the number of arbitrary constants in it. His most recent paper on arxiv from 2008, is entitled, "The New Symmetries Beyond the Standard Model (The Body-centred Cubic Periodic Symmetries in Particle Physics)" and provides simple formulas to calculate all quark and hadron masses to an accuracy of about 2%, similar to what QCD has achieved from first principles in the case of the proton and neutron. Another recent paper from Xu, from 2006, is "Using Phenomenological Formulae, Deducing the Masses and Flavors of the Quarks, Baryons and Mesons from Two Elementary Quarks". His work is in the same league of Koide's who phenomenological formula predicted the tau mass.
Another, less ambitious, published take on the same questions is found in E.F. Suisso; J.P.B.C. de Melo; T. Frederico, Ground state masses and binding energies of the nucleon, hyperon and heavy baryons in a light-front model (Braz. J. Phys. vol.33 no.2 São Paulo June 2003) http://dx.doi.org/10.1590/S0103-97332003000200028.
Amateur physicist Eliyahu Comay's blog "What's inside the proton?", also deserves credit for asking the right questions, although I lack the competence to evaluate his somewhat non-canonical approaches to answering those questions.
Are variety of background articles on QCD can be found here.
Good work along the same lines for the leptons is being done by scholars such as Ahmed Rashed, Alakabha Datta in "The charged lepton mass matrix and non-zero θ13 with TeV scale New Physics."
Another, less ambitious, published take on the same questions is found in E.F. Suisso; J.P.B.C. de Melo; T. Frederico, Ground state masses and binding energies of the nucleon, hyperon and heavy baryons in a light-front model (Braz. J. Phys. vol.33 no.2 São Paulo June 2003) http://dx.doi.org/10.1590/S0103-97332003000200028.
Amateur physicist Eliyahu Comay's blog "What's inside the proton?", also deserves credit for asking the right questions, although I lack the competence to evaluate his somewhat non-canonical approaches to answering those questions.
Are variety of background articles on QCD can be found here.
Good work along the same lines for the leptons is being done by scholars such as Ahmed Rashed, Alakabha Datta in "The charged lepton mass matrix and non-zero θ13 with TeV scale New Physics."
Monday, September 12, 2011
Genetic Links of Mon-Khmer and Hmong-Mien Peoples Confirmed
.
A PCA chart and branching tree cluster analysis of various Asian linguistic communities from the linked paper from PLOS that doesn't fully reproduce the conclusions reached by sublineage analysis in the cited paper.
An expanded study of Y-DNA population genetics in Southeast Asia by Chinese researchers, confirms that close genetic ties of Mon-Khmer (a.k.a. Austro-Asiatic when the Munda of India are also included) and Hmong-Mien peoples, at least in the patriline, focusing on the O3a3b-M7 Y-DNA haplogroup where the Mon-Khmer appearing at a basal position while Hmong-Mien and Tibeto-Burmese individuals with this hapologroup have subhaplogroups more on the fringes of this patriline tree. O3a3c1-M117, the dominant East Asian haplogroup shows a similar pattern. These haplogroups also corroborate the Southeast Asian origins of most of the East Asian Y-DNA patrilines.
Context
The study also provides a helpful contextualizing recap of prior findings about the population genetic history of East Eurasia.
There are 147 Mon-Khmer languages are spoken by more than 90 million people, mostly in Southeast Asia, of which the dominant languages of Vietnam, Laos and Cambodia are the best known (there are isolated pockets elsewhere).
There are 38 Hmong-Mien languages spoken by about 13 million people, of whom 12 million are in Southern China and the rest are in Southeast Asia, in separated linguistic islands across that region.
Sino-Tibetan languages (e.g. Chinese and Tibetan and Burmese) and Tai-Kendai languages (e.g. Thai) are also spoken in Southeast Asia, but are believed for multiple reasons historical, archaeological and genetic to be arrivals from the North and East in the last 3,000 years. Thus, Mon-Khmer and Hmong-Mien language speakers are likely to be more closely related to the aboriginal peoples of Southeast Asia.
The paper notes that 57% of East Asian men have some Y-DNA derivative of O3-M175, with subhaplogroups O3-M122, O2a-M95 and O1a-M119 all clearly entering East Asia from the south. As study of Hainan aboriginal people also concludes that while O1a-M119 and O2a-M95 probably arrived in East Asia via a coastal southern route in the east of East Asia, that O3-M122 probably entered East Asia by another route that could be revealed by study of the subhaplogroups of O3-M122. This study focused on exploring the origins of East Asian men whose patriline ancestors did not arrive in East Asia via a coastal southern route in the east of East Asia.
Key Conclusions
The abstract to the paper states:
A genetically based conclusion that the Hmong-Mien peoples are an offshoot of the Mon-Khmer peoples, something that linguistic analysis has not reached consensus upon, is a finding of considerable importance in parsing out the prehistory of Southeast Asia, even though the hypothesis that Mon-Khmer and Hmong-Mien both belong to a macrolinguistic family (sometimes called Yangtzean) has existed for some time as one of several efforts to link the languages of South China and Southeast Asia into linguistic macrofamilies.
If anything, linguistic geography, showing the Hmong-Mien to be scattered, while the Mon-Khmer had retained a more compact distribution had been argued to show the Hmong-Mien's greater antiquity, although this evidence itself is not very strong. The state of the academic discussion of linguistic origins is summed up in the Wikipedia article on the concept of Urheimat to which I have contributed.
Tai-Kadai languages also appear to be spoken by populations closely related to Mon-Khmer and Hmong-Mien peoples, although not quite so closely related as those two populations are to each other. The Austronesian language speakers, in contrast, who have their origins in the aboriginal peoples of Taiwan and possible their ancient coastal neighbors in South China, end up looking like something of an outgroup to the other three, and as an outgroup even to a group composed of the Mon-Khmer, Hmong-Mien, Tai-Kadai, and Sino-Tibetans, almost to the same extent as Altaic language speakers.
Details of the Y-DNA Haplogroup Findings
In addition to various haplogroup O Y-DNA types, there were a number of individuals in multiple subsets of the HM and MK language groups who had Y-DNA haplogroups C and F (which are a clade shared with O which is derived) and D1 (which is more closely related to the dominant African Y-DNA haplogroup E). Both C and D viewed to be among the earliest waves of modern human migration into Asia following the Out of Africa event.
Y-DNA haplogroup DE* was tested for and not found. One Hmong-Daw individual was found with Y-DNA haplogroup Q1a1 out of 51 individuals in that community, and P* was found in just two individuals and a total combined sample of 1,652 HM and MK individuals, outlier results that might indicate that these haplogroups associated with North Asian populations wasn't part of the aboriginal population at all. O1a2-M110 which is associated with Thai-Kadai population was found in only only Palyu sample of the four dozen groups studied, and the Palyu have historically had Kadai influence sometime in the last 3,000 years.
Mutation Dating
Given recent findings that cast serious doubt on Y-DNA mutation rate dating, the absolute time period estimates for this migration don't bear mention, although the conclusion that the most common Y-DNA haplogroups of Southeast Asia, O2a-M95 (which accounts for 87.18% MK men in the study and 45.16% of HM men in the study and is also common in the Munda and fairly common in Sino-Tibetan, Tai-Kendai and Austroasiatic populations) and O3-M122 (of which the two O3 haplogroups studies are subtypes that appear at high frequency in Mon-Khmer and Hmong-Mien but low frequency in other groups), are much older than the studied subhaplogroups is credible, as it the conclusion that the studied subhaplogroups are similar in age.
Aren't Autosomal Whole Genome Studies Better?
Autosomal whole genome studies have their place. They capture contributions from populations that patrilines and matrilines that make up only a small percentage of the genome miss and can be much more informative when sample sizes of populations old enough to have reached fixation of most of their population genetic gene frequenceis are studied. As the Gene Expression blog has recently demostrated with do it yourself genetic studies of one or two genomes from Tutsi and Malagasy populations, the difference between N=0 and N=1 or N=2 in whole genomes is immense. Studies of mtDNA and Y-DNA take much larger samples to be informative. But, mtDNA and Y-DNA branching tree analysis (i.e. phylogeny) is much more informative for questions of cause and effect that can show the direcetion of genetic links in a way that autosomal studies cannot.
Combined Y-DNA, mtDNA and autosomal DNA, in addition to historical records, linguistics, geography, artifacts, archaeclimate data, ancient DNA, and DNA studies of species like domesticated animals and food crops that were fellow travelers with prehistorical populations, are best, of course. And, Y-DNA alone always leaves open the question of whether there was a dominance or conquest settlement pattern, or patrilocal marriage patterns, that makes the Y-DNA patriline patterns significantly different from the mtDNA matriline patterns.
Frequently, as noted in a new paper cited in a recent post by Dienekes, where there is a discrepency, the Y-DNA patterns show more migration over long distances into different geographic zones while the matriline patterns are more representative of the indigeneous population. In an ideal world, we could link the Y-DNA, mtDNA and autosomal DNA patterns incorporating the other evidence to form a coherent picture of a rather complex story of prehistoric population migrations and admixtures, enhancing the credibility of all of the related lines of evidence. Linguistic history tend to more closely follows patrilines than matrilines, so Y-DNA phylogeny is more informative as a means of confirming linguistic phylogenies.
But, Y-DNA studies of patrilines of secondary frequency are quite informative for the purposes for which they are used in this study. Indeed, they are better for this purpose than autosomal data. Autosomal data could corroborate the close genetic relationship of the Mon-Khmer and Hmong-Mien peoples (or confound it), but could not show which population was most likely to have descended from the other. In contrast, an mtDNA study, if it confirmed the Y-DNA conclusion regarding the Mon-Khmer and Hmong-Mien peoples, would be particularly powerful and would also provide more accurate dating of the splits than Y-DNA dating can provide due to its inherently problematic issues such as loci that mutate at different rates.
Sources
The main paper is: Cai X, Qin Z, Wen B, Xu S, Wang Y, et al. (2011) Human Migration through Bottlenecks from Southeast Asia into East Asia during Last Glacial Maximum Revealed by Y Chromosomes. PLoS ONE 6(8): e24282. doi:10.1371/journal.pone.0024282
The paper cited by Dienekes is: Peter Forster, Colin Renfrew (2011) Mother Tongue and Y Chromosomes, Science 9 September 2011: Vol. 333 no. 6048 pp. 1390-1391 doi: 10.1126/science.1205331
A PCA chart and branching tree cluster analysis of various Asian linguistic communities from the linked paper from PLOS that doesn't fully reproduce the conclusions reached by sublineage analysis in the cited paper.
An expanded study of Y-DNA population genetics in Southeast Asia by Chinese researchers, confirms that close genetic ties of Mon-Khmer (a.k.a. Austro-Asiatic when the Munda of India are also included) and Hmong-Mien peoples, at least in the patriline, focusing on the O3a3b-M7 Y-DNA haplogroup where the Mon-Khmer appearing at a basal position while Hmong-Mien and Tibeto-Burmese individuals with this hapologroup have subhaplogroups more on the fringes of this patriline tree. O3a3c1-M117, the dominant East Asian haplogroup shows a similar pattern. These haplogroups also corroborate the Southeast Asian origins of most of the East Asian Y-DNA patrilines.
Context
The study also provides a helpful contextualizing recap of prior findings about the population genetic history of East Eurasia.
There are 147 Mon-Khmer languages are spoken by more than 90 million people, mostly in Southeast Asia, of which the dominant languages of Vietnam, Laos and Cambodia are the best known (there are isolated pockets elsewhere).
There are 38 Hmong-Mien languages spoken by about 13 million people, of whom 12 million are in Southern China and the rest are in Southeast Asia, in separated linguistic islands across that region.
Sino-Tibetan languages (e.g. Chinese and Tibetan and Burmese) and Tai-Kendai languages (e.g. Thai) are also spoken in Southeast Asia, but are believed for multiple reasons historical, archaeological and genetic to be arrivals from the North and East in the last 3,000 years. Thus, Mon-Khmer and Hmong-Mien language speakers are likely to be more closely related to the aboriginal peoples of Southeast Asia.
The paper notes that 57% of East Asian men have some Y-DNA derivative of O3-M175, with subhaplogroups O3-M122, O2a-M95 and O1a-M119 all clearly entering East Asia from the south. As study of Hainan aboriginal people also concludes that while O1a-M119 and O2a-M95 probably arrived in East Asia via a coastal southern route in the east of East Asia, that O3-M122 probably entered East Asia by another route that could be revealed by study of the subhaplogroups of O3-M122. This study focused on exploring the origins of East Asian men whose patriline ancestors did not arrive in East Asia via a coastal southern route in the east of East Asia.
Key Conclusions
The abstract to the paper states:
These patterns indicate an early unidirectional diffusion from Southeast Asia into East Asia, which might have resulted from the genetic drift of East Asian ancestors carrying these two haplogroups through many small bottle-necks formed by the complicated landscape between Southeast Asia and East Asia. The ages of O3a3b-M7 and O3a3c1-M117 were . . . followed by the emergence of the ancestors of HM lineages out of MK and the unidirectional northward migrations into East Asia.The study also briefly, and without much in the way of helpful illustrations with maps, speculates on the geographic conditions in pre-history that could have shaped these developments and the paths these peoples could have taken from Southeast Asia into China.
A genetically based conclusion that the Hmong-Mien peoples are an offshoot of the Mon-Khmer peoples, something that linguistic analysis has not reached consensus upon, is a finding of considerable importance in parsing out the prehistory of Southeast Asia, even though the hypothesis that Mon-Khmer and Hmong-Mien both belong to a macrolinguistic family (sometimes called Yangtzean) has existed for some time as one of several efforts to link the languages of South China and Southeast Asia into linguistic macrofamilies.
If anything, linguistic geography, showing the Hmong-Mien to be scattered, while the Mon-Khmer had retained a more compact distribution had been argued to show the Hmong-Mien's greater antiquity, although this evidence itself is not very strong. The state of the academic discussion of linguistic origins is summed up in the Wikipedia article on the concept of Urheimat to which I have contributed.
Tai-Kadai languages also appear to be spoken by populations closely related to Mon-Khmer and Hmong-Mien peoples, although not quite so closely related as those two populations are to each other. The Austronesian language speakers, in contrast, who have their origins in the aboriginal peoples of Taiwan and possible their ancient coastal neighbors in South China, end up looking like something of an outgroup to the other three, and as an outgroup even to a group composed of the Mon-Khmer, Hmong-Mien, Tai-Kadai, and Sino-Tibetans, almost to the same extent as Altaic language speakers.
Details of the Y-DNA Haplogroup Findings
In addition to various haplogroup O Y-DNA types, there were a number of individuals in multiple subsets of the HM and MK language groups who had Y-DNA haplogroups C and F (which are a clade shared with O which is derived) and D1 (which is more closely related to the dominant African Y-DNA haplogroup E). Both C and D viewed to be among the earliest waves of modern human migration into Asia following the Out of Africa event.
Y-DNA haplogroup DE* was tested for and not found. One Hmong-Daw individual was found with Y-DNA haplogroup Q1a1 out of 51 individuals in that community, and P* was found in just two individuals and a total combined sample of 1,652 HM and MK individuals, outlier results that might indicate that these haplogroups associated with North Asian populations wasn't part of the aboriginal population at all. O1a2-M110 which is associated with Thai-Kadai population was found in only only Palyu sample of the four dozen groups studied, and the Palyu have historically had Kadai influence sometime in the last 3,000 years.
Mutation Dating
Given recent findings that cast serious doubt on Y-DNA mutation rate dating, the absolute time period estimates for this migration don't bear mention, although the conclusion that the most common Y-DNA haplogroups of Southeast Asia, O2a-M95 (which accounts for 87.18% MK men in the study and 45.16% of HM men in the study and is also common in the Munda and fairly common in Sino-Tibetan, Tai-Kendai and Austroasiatic populations) and O3-M122 (of which the two O3 haplogroups studies are subtypes that appear at high frequency in Mon-Khmer and Hmong-Mien but low frequency in other groups), are much older than the studied subhaplogroups is credible, as it the conclusion that the studied subhaplogroups are similar in age.
Aren't Autosomal Whole Genome Studies Better?
Autosomal whole genome studies have their place. They capture contributions from populations that patrilines and matrilines that make up only a small percentage of the genome miss and can be much more informative when sample sizes of populations old enough to have reached fixation of most of their population genetic gene frequenceis are studied. As the Gene Expression blog has recently demostrated with do it yourself genetic studies of one or two genomes from Tutsi and Malagasy populations, the difference between N=0 and N=1 or N=2 in whole genomes is immense. Studies of mtDNA and Y-DNA take much larger samples to be informative. But, mtDNA and Y-DNA branching tree analysis (i.e. phylogeny) is much more informative for questions of cause and effect that can show the direcetion of genetic links in a way that autosomal studies cannot.
Combined Y-DNA, mtDNA and autosomal DNA, in addition to historical records, linguistics, geography, artifacts, archaeclimate data, ancient DNA, and DNA studies of species like domesticated animals and food crops that were fellow travelers with prehistorical populations, are best, of course. And, Y-DNA alone always leaves open the question of whether there was a dominance or conquest settlement pattern, or patrilocal marriage patterns, that makes the Y-DNA patriline patterns significantly different from the mtDNA matriline patterns.
Frequently, as noted in a new paper cited in a recent post by Dienekes, where there is a discrepency, the Y-DNA patterns show more migration over long distances into different geographic zones while the matriline patterns are more representative of the indigeneous population. In an ideal world, we could link the Y-DNA, mtDNA and autosomal DNA patterns incorporating the other evidence to form a coherent picture of a rather complex story of prehistoric population migrations and admixtures, enhancing the credibility of all of the related lines of evidence. Linguistic history tend to more closely follows patrilines than matrilines, so Y-DNA phylogeny is more informative as a means of confirming linguistic phylogenies.
But, Y-DNA studies of patrilines of secondary frequency are quite informative for the purposes for which they are used in this study. Indeed, they are better for this purpose than autosomal data. Autosomal data could corroborate the close genetic relationship of the Mon-Khmer and Hmong-Mien peoples (or confound it), but could not show which population was most likely to have descended from the other. In contrast, an mtDNA study, if it confirmed the Y-DNA conclusion regarding the Mon-Khmer and Hmong-Mien peoples, would be particularly powerful and would also provide more accurate dating of the splits than Y-DNA dating can provide due to its inherently problematic issues such as loci that mutate at different rates.
Sources
The main paper is: Cai X, Qin Z, Wen B, Xu S, Wang Y, et al. (2011) Human Migration through Bottlenecks from Southeast Asia into East Asia during Last Glacial Maximum Revealed by Y Chromosomes. PLoS ONE 6(8): e24282. doi:10.1371/journal.pone.0024282
The paper cited by Dienekes is: Peter Forster, Colin Renfrew (2011) Mother Tongue and Y Chromosomes, Science 9 September 2011: Vol. 333 no. 6048 pp. 1390-1391 doi: 10.1126/science.1205331
Friday, September 9, 2011
A good background paper on the Higgs Boson search
Matt Strassler has a nice, current as of September 2011, post up providing background on the Higgs boson search in the context of half a dozen different theoretical models. The outline is as follows:
"1.The Standard Model Higgs particle
2.A Standard Model Higgs sector but with Other New Particles
3.The case of two Higgs particles
4.The case of five Higgs particles
5.Supersymmetry: Five Higgs particles along with superpartners [new!]
6.No Higgs particle (to speak of) [new!]"
"1.The Standard Model Higgs particle
2.A Standard Model Higgs sector but with Other New Particles
3.The case of two Higgs particles
4.The case of five Higgs particles
5.Supersymmetry: Five Higgs particles along with superpartners [new!]
6.No Higgs particle (to speak of) [new!]"
Xenon 100 addresses dark matter signals in other experiments
A new paper by David B. Cline (posted yesterday at arxiv.og) from the Xenon 100 experiment addresses the purported dark matter signals in other direct detection dark matter experiments (including CRESS) that its results seem to rule out. While not quite a battle of blog posts, the arxiv discussion is going on at a pace much faster than debates are carried out in printed journals. As the abstract to this article explains:
The suggesting of other sources for season variation in underground laboratory results is a major contribution to the debate. The crux of the matter is that:
Nothing indicates the limitations of self-estimated error bars more than conflicting contemporaneous experiments conducted by groups of professional physicists that show the existence or non-existence of the same thing to considerable statistical significance.
My prediction is that the CoGeNT, CRESST and DAMA experimental evidence for the low WIMP mass hypothesis, which is not necessarily even entirely consistent between the experiments, will ultimately be found to have been premature and attributed to other causes in the background that were not accounted for in the initial analysis. But, I'd be delighted to be wrong and see "new physics" discovered instead.
See also more discussion here.
We review the confused situation concerning evidence for low-mass WIMPs. In the past one half year there have been new results concerning the existence of WIMPs at low mass including the new XENON 100, 100-day data, additional CDMS results, the publication of annual variation data from LVD and Borexino and new CoGeNT data. Along with the S2 analyses of the XENON 10 data we provide an overview of this situation. We discuss new results from 2011 here. We also discuss the origin of annual variations of signals in underground laboratories.
This article is meant to be an update of recent experimental results. It is not a critical comparison of the claims of various experimental groups. Such critiques are made in public conferences and meetings. There is currently an intense discussion being carried out about the low mass WIMP region with many different viewpoints. We have little to say about this situation except that the scientific method usually insures the correct results will eventually surface.
The suggesting of other sources for season variation in underground laboratory results is a major contribution to the debate. The crux of the matter is that:
The authors of CoGeNT, CRESST, and DAMA indicate that the three experiments show the evidence for low-mass WIMPs. However the DAMA results are excluded by two CDMS experiments. Therefore three to four independent experiments exclude the low WIMP mass hypothesis.
Nothing indicates the limitations of self-estimated error bars more than conflicting contemporaneous experiments conducted by groups of professional physicists that show the existence or non-existence of the same thing to considerable statistical significance.
My prediction is that the CoGeNT, CRESST and DAMA experimental evidence for the low WIMP mass hypothesis, which is not necessarily even entirely consistent between the experiments, will ultimately be found to have been premature and attributed to other causes in the background that were not accounted for in the initial analysis. But, I'd be delighted to be wrong and see "new physics" discovered instead.
See also more discussion here.
Thursday, September 8, 2011
Doubts About COGENT and DAMA Dark Matter Results
From a comment at Resonaances:
Both the results reduce the apparent convergence around 10 GeV of mass of results between COGENT, DAMA and CRESS, the three experiments that have seen what could have been direct dark matter detection signals.
JK said...
Also interesting in this context is the CoGeNT talk at TAUP: http://taup2011.mpp.mpg.de/php/downloadPresentationFile.php?type=presentation&sessionid=5&presentationid=280
According to that talk part of the CoGeNT excess is probably due to surface backgrounds. Effectively, this moves the CoGeNT-allowed region to higher masses and smaller cross sections.
Also, Collar & company have re-measured quenching factors in NaI(Tl) (DAMA's target material). According to their results, which are in some tension with older measurements, the quenching factor for Na recoils is *smaller* than what was assumed by DAMA. This would move the DAMA-allowed region to the right.
So, the picture of DM direct detection has changed quite a bit this week, but it looks still as confusing as ever.
8 September 2011 13:55
Both the results reduce the apparent convergence around 10 GeV of mass of results between COGENT, DAMA and CRESS, the three experiments that have seen what could have been direct dark matter detection signals.
Wednesday, September 7, 2011
African Archaic Admixture Recap
Razib, as usual, has a nice digest of the discovery that in Africa anatomically modern humans (our primary genetic ancestors) had sex with archaic hominins (roughly congruent with Homo Erectus), leaving some traces of the archaic hominins in the genes of some Africans today.
From here.
The African outgroups with the highest levels of archaic admixture (whose absolute numbers are small, perhaps in the hundreds of thousands, and are a very small proportion of all Africans, perhaps 0.1% of all Africans) became distinct populations of modern humans around the time of the main Out of Africa event or perhaps a couple tens of thousands of years earlier.
The lowest levels of ancient admixture appear to be populations where Y-DNA haplogroup E and mtDNA haplogroups L2 and L3 are most common, a group that includes the African contribution to almost all African Americans in the United States.
This adds to the recent discoveries based on comparisons with ancient DNA that Melanesians and people from populations with some Melanesian ancestry seem to have significant levels of admixture with a population known genetically today called the Denisovians who left genetic traces in Southern Siberia, and that all Eurasians have a small but significant proportion Neanderthal ancestry, with immune system genes seeming to have an outsized contribution and the European and Asian inheritances from Neanderthals being mostly disjoint.
The Denisovian admixture presumably took place close in time to the modern human settlement of Melanesia, around 45,000 to 50,000 years ago. Denisovians aren't clearly identified with a particular species of archaic hominins, although Neanderthals, late stage Homo Erectus and "Hobbits", or some hybrid of these, are the main potential contenders in the relevant time frame. The number of people with significant Denisovian admixture today probably numbers in the tens of millions or perhaps the low hundreds of millions.
Neanderthals went extinct around 30,000 years ago, but a very large share of European ancestry dates to sometime after the Last Glacial Maximum ca. 20,000 years ago, after which Europe was repopulated from outside Europe and from a few refugia in Southern Europe. Thus, even if Upper Paleolithic modern humans in Europe (the Cro-Magnons) had elevated levels of Neanderthal admixture, they may have been mostly replaced or diluted beyond recognition by subsequent population waves in much of Europe.
The fact that both modern Asians and modern Europeans have similar levels of Neanderthal admixture, but that their Neanderthal legacies don't overlap much, suggests that Neanderthal admixture probably happened mostly in or near the Near East not long after the Out of Africa event, or possibly even during a "false start" Out of Africa event ca. 100,000 to 75,000 years ago that mostly fizzled with the first wave either dying out or retreating to refugia either in Africa (probably in the Northeast if there) or outside of Africa (Arabia and South Asia are strong possibilities) until a more successful Out of Africa event ca. 50,000 years ago that started the colonization of Europe.
Best guesses of the period of archaic hominin and modern human interaction in any one place are on the order of 1,000 to 2,000 years where estimates are possible, but the expanding frontiers of modern humans meant that someone, somewhere there were archaic hominin/modern human interactions for tens of thousands of years in modern human history. The Hobbits of Flores are the last documented archaic hominins to persist, perishing ca. 18,000 years ago. But, archaic hominins were extinct everywhere long before agriculture, stable decent sized towns, domesticated animals other than dogs, or other hallmarks of modern society arose. Indeed, at the time of archaic admixture modern human racial divisions were just starting to emerge.
The first farmers in the Danube and the hunter-gatherers that they displaced, numerically overwhelmed and absorbed, or caused the death of (either directly or due to resource conflicts) would have been as different in appearance as an Australian aborigine and a typical citizen of France. Immense human genetic diversity from the hunter-gatherer era across the world was wiped out as farming populations expanded. Their overlap as co-existing populations was also probably on the order of a thousand years in any one place.
Neanderthals flourished after the hominin species such as Homo Erectus who are likely sources of archaic admixture with Africans became distinct and before modern humans.
There are no Y-DNA or mtDNA contributions to archaic hominins in anyone. No one on Earth has an ultimate matriline ancestor or patriline ancestor who is an archaic human who lived after the common ancestors of all modern humans.
Biblical references to admixtures of humans with "giants" and angels (one of which is quoted by Razib in his post) seem unlikely to derive from these ancient admixture events that would have taken place not less than 26,000 years before writing was invented and probably 20,000 years before any of the major language families in the world today existed, leaving hundreds of generations across many, many languages that oral histories would have to survive though in a society that wandered the Earth in small bands in which people had average life expectencies on the order of 40 years or less. Goliath, for example, was probably a Mycenian Greek relocated to the Levant following the Bronze Age collapse, if there is any historical basis to that story.
Pygmies and Khoisan have admixture from a distinct population at the level of ~2%. This population diverged from the other ~98% of their ancestry ~700,000 years before the present, and the hybridization occurred ~30-40,000 years before the present. Most other African groups have only traces of this element, with some West Africans lacking it. . . . Mbuti Pygmies of the eastern Congo likely have a special place in this possible admixture event. In particular, they seem to possess the diverged variants found in the western Pygmies, the Biaka, and the Khoisan populations of southern Africa. As assumed the pattern of admixture seems to be such that the two Pygmy groups and the Khoisan exhibit elevated signatures of archaic contributions, while other African groups manifest admixture in direct proportion to their known admixture to the aforementioned populations. For example, the Bantu group with the highest proportion of admixture are the Xhosa, who also have the most Khoisan ancestry of non-Khoisan populations. The West African Mandenka seem to have trivial admixture from this archaic group.
From here.
The African outgroups with the highest levels of archaic admixture (whose absolute numbers are small, perhaps in the hundreds of thousands, and are a very small proportion of all Africans, perhaps 0.1% of all Africans) became distinct populations of modern humans around the time of the main Out of Africa event or perhaps a couple tens of thousands of years earlier.
The lowest levels of ancient admixture appear to be populations where Y-DNA haplogroup E and mtDNA haplogroups L2 and L3 are most common, a group that includes the African contribution to almost all African Americans in the United States.
This adds to the recent discoveries based on comparisons with ancient DNA that Melanesians and people from populations with some Melanesian ancestry seem to have significant levels of admixture with a population known genetically today called the Denisovians who left genetic traces in Southern Siberia, and that all Eurasians have a small but significant proportion Neanderthal ancestry, with immune system genes seeming to have an outsized contribution and the European and Asian inheritances from Neanderthals being mostly disjoint.
The Denisovian admixture presumably took place close in time to the modern human settlement of Melanesia, around 45,000 to 50,000 years ago. Denisovians aren't clearly identified with a particular species of archaic hominins, although Neanderthals, late stage Homo Erectus and "Hobbits", or some hybrid of these, are the main potential contenders in the relevant time frame. The number of people with significant Denisovian admixture today probably numbers in the tens of millions or perhaps the low hundreds of millions.
Neanderthals went extinct around 30,000 years ago, but a very large share of European ancestry dates to sometime after the Last Glacial Maximum ca. 20,000 years ago, after which Europe was repopulated from outside Europe and from a few refugia in Southern Europe. Thus, even if Upper Paleolithic modern humans in Europe (the Cro-Magnons) had elevated levels of Neanderthal admixture, they may have been mostly replaced or diluted beyond recognition by subsequent population waves in much of Europe.
The fact that both modern Asians and modern Europeans have similar levels of Neanderthal admixture, but that their Neanderthal legacies don't overlap much, suggests that Neanderthal admixture probably happened mostly in or near the Near East not long after the Out of Africa event, or possibly even during a "false start" Out of Africa event ca. 100,000 to 75,000 years ago that mostly fizzled with the first wave either dying out or retreating to refugia either in Africa (probably in the Northeast if there) or outside of Africa (Arabia and South Asia are strong possibilities) until a more successful Out of Africa event ca. 50,000 years ago that started the colonization of Europe.
Best guesses of the period of archaic hominin and modern human interaction in any one place are on the order of 1,000 to 2,000 years where estimates are possible, but the expanding frontiers of modern humans meant that someone, somewhere there were archaic hominin/modern human interactions for tens of thousands of years in modern human history. The Hobbits of Flores are the last documented archaic hominins to persist, perishing ca. 18,000 years ago. But, archaic hominins were extinct everywhere long before agriculture, stable decent sized towns, domesticated animals other than dogs, or other hallmarks of modern society arose. Indeed, at the time of archaic admixture modern human racial divisions were just starting to emerge.
The first farmers in the Danube and the hunter-gatherers that they displaced, numerically overwhelmed and absorbed, or caused the death of (either directly or due to resource conflicts) would have been as different in appearance as an Australian aborigine and a typical citizen of France. Immense human genetic diversity from the hunter-gatherer era across the world was wiped out as farming populations expanded. Their overlap as co-existing populations was also probably on the order of a thousand years in any one place.
Neanderthals flourished after the hominin species such as Homo Erectus who are likely sources of archaic admixture with Africans became distinct and before modern humans.
There are no Y-DNA or mtDNA contributions to archaic hominins in anyone. No one on Earth has an ultimate matriline ancestor or patriline ancestor who is an archaic human who lived after the common ancestors of all modern humans.
Biblical references to admixtures of humans with "giants" and angels (one of which is quoted by Razib in his post) seem unlikely to derive from these ancient admixture events that would have taken place not less than 26,000 years before writing was invented and probably 20,000 years before any of the major language families in the world today existed, leaving hundreds of generations across many, many languages that oral histories would have to survive though in a society that wandered the Earth in small bands in which people had average life expectencies on the order of 40 years or less. Goliath, for example, was probably a Mycenian Greek relocated to the Levant following the Bronze Age collapse, if there is any historical basis to that story.
Intuitions on General Relativity As MOND
Galactic rotation curves, gravitational lensing, and the kinematic behavior of galactic clusters all point to the existence of substantial amounts of dark matter beyond the matter that can be inferred from the light we detect from stars and the black holes that we infer are at the centers of galaxies and certain other systems.
But, the dominant cold dark matter paradigm has pretty much been disproven by observation and experiment. Cold dark matter doesn't arrange itself the way it needs to in order to produce the observed results.
Well, dark matter is one way to reconcile what we see with the models of gravity we use to predict how these systems will behave. Basically, at the galactic scale the field strength of gravity does not fall off in a 1/r^2 manner the way that it should from the matter distributions that we can observe or infer from patterns of starlight we can see. After a critical value of gravitational field strength called a0, we observe galactical scale gravity falling off at a 1/r rate instead. We see the same thing in wide orbit binary stars.
A theory called MOND simply applied the phenomenological gravity law that this was the case and was able to predict almost all galactic scale gravity behavior, predict the amount of dark matter present in previously untested systems and its distribution, and the wide orbit binary star behavior with accuracy with this one constant and a simple modified Newtonian gravity equation.
The simple version of MOND is inconsistent with General Relativity where it matters, but it succeptible to being generalized to a formula that reduces to General Relativity. Several similar theories have also been proposed.
But, maybe General Relativity is good enough on its own. A recent discovery that the amount of ordinary matter in eliptical galaxies has greatly underestimated reduced the amount of dark matter to be explained from a roughly 3-1 dark to visible ratio to a roughly 1-1 dark to visible ratio. And, most early models at the galactic scale simple used Newtonian gravity without corrections for General Relativity.
Efforts to describe galaxies with full fledged General Relativity have revealed that much of the unexplained dark matter that seems to be there when a Newtonian approximation is used disappears when full fledged General Relativity is used. Not all of it, but a lot of it.
Also notably, the large scale structure of the universe appears to be indifferent to the proportions of dark matter and ordinary matter contained in them.
Some basic intuitions, stated in less technical form, about what is going on, follow:
1. Gravitational effects in General Relativity are a function of five vectors and a scalar that go into the stress-energy tensor. Both General Relativity and Newtonian gravity reference the scalar of rest mass. But, General Relativity adds three element vectors (corresponding to the three dimensions of space) all of which are derivatives with respect to time, for (1) linear momentum, (2) angular momentum, (3) special relativistic boost momentum, (4) pressure, and (5) energy flux.
2. In galactic cases, where MOND works, it is possible to choose a frame of reference where linear momentum is zero or nearly zero, the speeds involved make the special relativistic boosts trivial relative to other factors even in the weak field, pressure is nearly spherically symmetric, and energy flux (mostly from emitted photons from stars) is nearly spherically symmetrc. But, angular momentum is not spherically symmetric in a galaxy or wide orbit binary star and makes a non-trivial contribution relative to rest mass. Angular momentum is basically all in a two-dimensional circular direction in a galaxy or binary star system, so it make sense that unlike the spherically symmetrical and scalar parts of gravity, which fall off as 1/r^2 which corresponds to the surface of a sphere (4/3(pi)r^2) that angular momentum effects would fall of as 1/r which corresponds to the circumference of a circle (2(pi)r).
3. a0 makes sense if the structure of the systems where MOND works have a similar relationship between mass distribution with Newtonian gravity relative to angular momentum relative to the component of gravity in General Relativity due to the angular momentum component of the stres-energy tensor. Some of this flows from the formulas for angular momentum and general relativistic gravity, but some of this flows from the dynamical process by which galaxies form which shows strong evidence of structure (there are two main distinct types - spiral and elliptical, they have non-overlapping mass ranges, they have similar structures within each category, there is a maximum galaxy size).
4. A phenomenological test that would distinguish dark matter and MOND theories which are generically spherically symmetric, from full general relativity calculations (too complex for anyone to have done exactly), is that in a general relativity extension, MOND/Dark matter effects should not be visible in parts of the weak gravitational field that are at a high azimuthal angle relative to the two dimensional plane in which the galaxy rotates. Neither MOND theories nor dark matter could explain a discrepancy of this type with any confidence, while general relativity could. It ought to be not terribly difficult to make a few observations along this line.
5. The exceptions to MOND success are also suggestive. The Bullet Cluster, which is the classic counterproof of MOND-like theories, is the only really decisive example of a gravitational system where linear momentum is important in every frame of reference relative to rest mass and angular momentum, complicating the analysis in full general relativity greatly. Galactic clusters have two layers of angular momentum at work - intragalactic and the angular momentum involved in the relative motion of the different galaxies in the cluster, and may have unusually matter density profiles that give rise to asymmetric pressure profiles. There is no nice neat pattern for galactic clusters as there is for galaxies themselves so the analysis is more involved.
Of course, it would also be quite impressive if General Relativity, almost a century after it was formulated in 1916, was discovered through better calculations of its effects in more complex systems to account for both dark matter in the absence of quantum gravity corrections, as well as accounting for dark energy as it already does (via the cosmological constant) with the dark matter proving to be simply a huge theoretical error and an ordinary matter counting shortfall. And, this would eliminate the need for particle physics to discover some dark matter candidate that could fit the bill, which would be nice, because particle physics is running out of options that fit the experimental data that put a number of constraints of dark matter's behavior. This would make the agenda for quantum gravity a quite modest one; we would only need it where quantum mechanics and general relativity are both relevant.
Even if unaccounted for ordinary matter and the non-Newtonian effects of General Relativity don't eliminate the need for all dark matter to explain what is observed, a reduced quantity of dark matter to account for could ease strains on particle physicists to find a plausible dark matter candidate and strains on cosmologists to figure out where the dark matter could have come from after the Big Bang.
But, the dominant cold dark matter paradigm has pretty much been disproven by observation and experiment. Cold dark matter doesn't arrange itself the way it needs to in order to produce the observed results.
Well, dark matter is one way to reconcile what we see with the models of gravity we use to predict how these systems will behave. Basically, at the galactic scale the field strength of gravity does not fall off in a 1/r^2 manner the way that it should from the matter distributions that we can observe or infer from patterns of starlight we can see. After a critical value of gravitational field strength called a0, we observe galactical scale gravity falling off at a 1/r rate instead. We see the same thing in wide orbit binary stars.
A theory called MOND simply applied the phenomenological gravity law that this was the case and was able to predict almost all galactic scale gravity behavior, predict the amount of dark matter present in previously untested systems and its distribution, and the wide orbit binary star behavior with accuracy with this one constant and a simple modified Newtonian gravity equation.
The simple version of MOND is inconsistent with General Relativity where it matters, but it succeptible to being generalized to a formula that reduces to General Relativity. Several similar theories have also been proposed.
But, maybe General Relativity is good enough on its own. A recent discovery that the amount of ordinary matter in eliptical galaxies has greatly underestimated reduced the amount of dark matter to be explained from a roughly 3-1 dark to visible ratio to a roughly 1-1 dark to visible ratio. And, most early models at the galactic scale simple used Newtonian gravity without corrections for General Relativity.
Efforts to describe galaxies with full fledged General Relativity have revealed that much of the unexplained dark matter that seems to be there when a Newtonian approximation is used disappears when full fledged General Relativity is used. Not all of it, but a lot of it.
Also notably, the large scale structure of the universe appears to be indifferent to the proportions of dark matter and ordinary matter contained in them.
Some basic intuitions, stated in less technical form, about what is going on, follow:
1. Gravitational effects in General Relativity are a function of five vectors and a scalar that go into the stress-energy tensor. Both General Relativity and Newtonian gravity reference the scalar of rest mass. But, General Relativity adds three element vectors (corresponding to the three dimensions of space) all of which are derivatives with respect to time, for (1) linear momentum, (2) angular momentum, (3) special relativistic boost momentum, (4) pressure, and (5) energy flux.
2. In galactic cases, where MOND works, it is possible to choose a frame of reference where linear momentum is zero or nearly zero, the speeds involved make the special relativistic boosts trivial relative to other factors even in the weak field, pressure is nearly spherically symmetric, and energy flux (mostly from emitted photons from stars) is nearly spherically symmetrc. But, angular momentum is not spherically symmetric in a galaxy or wide orbit binary star and makes a non-trivial contribution relative to rest mass. Angular momentum is basically all in a two-dimensional circular direction in a galaxy or binary star system, so it make sense that unlike the spherically symmetrical and scalar parts of gravity, which fall off as 1/r^2 which corresponds to the surface of a sphere (4/3(pi)r^2) that angular momentum effects would fall of as 1/r which corresponds to the circumference of a circle (2(pi)r).
3. a0 makes sense if the structure of the systems where MOND works have a similar relationship between mass distribution with Newtonian gravity relative to angular momentum relative to the component of gravity in General Relativity due to the angular momentum component of the stres-energy tensor. Some of this flows from the formulas for angular momentum and general relativistic gravity, but some of this flows from the dynamical process by which galaxies form which shows strong evidence of structure (there are two main distinct types - spiral and elliptical, they have non-overlapping mass ranges, they have similar structures within each category, there is a maximum galaxy size).
4. A phenomenological test that would distinguish dark matter and MOND theories which are generically spherically symmetric, from full general relativity calculations (too complex for anyone to have done exactly), is that in a general relativity extension, MOND/Dark matter effects should not be visible in parts of the weak gravitational field that are at a high azimuthal angle relative to the two dimensional plane in which the galaxy rotates. Neither MOND theories nor dark matter could explain a discrepancy of this type with any confidence, while general relativity could. It ought to be not terribly difficult to make a few observations along this line.
5. The exceptions to MOND success are also suggestive. The Bullet Cluster, which is the classic counterproof of MOND-like theories, is the only really decisive example of a gravitational system where linear momentum is important in every frame of reference relative to rest mass and angular momentum, complicating the analysis in full general relativity greatly. Galactic clusters have two layers of angular momentum at work - intragalactic and the angular momentum involved in the relative motion of the different galaxies in the cluster, and may have unusually matter density profiles that give rise to asymmetric pressure profiles. There is no nice neat pattern for galactic clusters as there is for galaxies themselves so the analysis is more involved.
Of course, it would also be quite impressive if General Relativity, almost a century after it was formulated in 1916, was discovered through better calculations of its effects in more complex systems to account for both dark matter in the absence of quantum gravity corrections, as well as accounting for dark energy as it already does (via the cosmological constant) with the dark matter proving to be simply a huge theoretical error and an ordinary matter counting shortfall. And, this would eliminate the need for particle physics to discover some dark matter candidate that could fit the bill, which would be nice, because particle physics is running out of options that fit the experimental data that put a number of constraints of dark matter's behavior. This would make the agenda for quantum gravity a quite modest one; we would only need it where quantum mechanics and general relativity are both relevant.
Even if unaccounted for ordinary matter and the non-Newtonian effects of General Relativity don't eliminate the need for all dark matter to explain what is observed, a reduced quantity of dark matter to account for could ease strains on particle physicists to find a plausible dark matter candidate and strains on cosmologists to figure out where the dark matter could have come from after the Big Bang.
Tuesday, September 6, 2011
Preons Plus LQG
An interesting preon formulation based on braided preons that would make up all fundamental particles embedded in a loop quantum gravity theory is explored at length, but not completed, in a recent paper by one of the oldest of the preon theorists and some co-authors in an August 31, 2011 preprint.
Muonic Hydrogen Revisited
Why is the Lamb shift in muonic hydrogen five sigma (which is an absolute error of 4%) different from the predicted value? (Muonic hydrogen is smaller than predicted by QED.)
One answer, according to a pre-print by a Spanish physicist (Antonio Pineda), may be that there are subtle issues in the calculation of polarization effects that show up on muonic hydrogen calculations which must be about 200 times as precise as those for proton size calculations in ordinary hydrogen.
Still, the issue deserves attention as it is one of the only five sigma or greater deviations from a Standard Model prediction that is out there.
One answer, according to a pre-print by a Spanish physicist (Antonio Pineda), may be that there are subtle issues in the calculation of polarization effects that show up on muonic hydrogen calculations which must be about 200 times as precise as those for proton size calculations in ordinary hydrogen.
Still, the issue deserves attention as it is one of the only five sigma or greater deviations from a Standard Model prediction that is out there.
Dementia Deadly?
Nearly 4,000 people between the ages of 60 to 102 years, initially seen from 1991 to 1993 by primary care physicians at Wishard Health Services, a large public hospital with community health centers in Indianapolis, participated in the study. The patients were followed for 13 years. . . . The study followed 3,957 patients. At screening, 3,157 had no cognitive impairment, 533 had mild impairment, and 267 had moderate to severe impairment. During follow-up, 57 percent of patients with no impairment died, compared with 68 percent of those with mild impairment and 79 percent of those with moderate to severe impairment. Median survival time was 138 months for patients with no impairment, 106 months for those with mild impairment, and 63 months for those with moderate to severe impairment.
Study participants were screened for cognitive impairment using an easy-to-administer 10-question mental status questionnaire. On the basis of the number of errors patients made on this test, they were categorized as having no, mild, or moderate to severe cognitive impairment. . . . Cognitive impairment affects memory and thinking. Approximately 4 million to 5 million people in the United States have dementia, and the number of individuals affected is significantly higher if individuals with milder forms of cognitive impairment are included.
From here.
Cause and effect aren't necessarily easy to separate here because dementia is a well documented consequence of the aging process and the aging process also tends to bring a parade of horribles. It might be partially accurate to see the onset of dementia as a general indicator of the extent to which a person is suffering from geriatric disorders, although there are certainly many ways that cognitive impairment can causally lead to bodily harm.
10 GeV Dark Matter?
The CRESST-II dark matter search thinks it may have observed dark matter particles with masses in the vicinity of 10 GeV (about 2-3 times the mass of a bottom quark and about six times the mass of a charged lepton of the tau variety), which is in the vicinity of other searches that claim to have seen dark matter, but not precisely overlapping, or perhaps about 25 GeV. Several other searches claim to have ruled out the dark matter that the other experiments claim to have seen.
Of course, these searches present all sorts of questions. Why do some searches see something at close to a four sigma level, while others rule out the same thing to similar degrees of certainty?
If we are seeing something, why are we seeing particles at masses that have been pretty definitively ruled out by precision measurements of weak force decays and neutrino searches? There shouldn't be anything, either a fundamental particle or a composite one, between bottom quark mass (between 4 and 5 GeV) and 40 GeV that interacts with the electromagnetic or weak force or is quark or includes a quark or is a Standard Model Higgs Boson. Certainly, nothing in the Standard Model fits. All known baryons and all known mesons are too light, topping out at about 5 GeV, apart from a couple of bottom-bottom quark possibilities, and the bottom-bottom quark mesons would be extremely unstable, making them poor dark matter candidates. (Top quarks at 173 GeV are too heavy in addition to being unstable.)
One could imagine, without stretching the Standard Model too far, right handed neutrinos whose masses are many orders of magnitude heavier than their left handed cousins. Glueballs aren't entirely ruled out, but don't seem like a very good fit either. Ground state glueballs should have much lower masses and even if they might be stable in a ground state, they probably wouldn't be stable at higher mass excited states. They are also predicted to get lighter as they gain momentum. Other exotic mesons are also a poor fit.
There are also good theoretical grounds to think that a graviton, if one exists, has no mass.
Even SUSY particles in most of the less ambitious versions of that theory (including the SUSY Higgs boson), are ruled out in that mass range by collider experiments, although Lubos holds out hope for a photino or bino. Gordon Kane, a strong SUSY supporter, hasn't seriously proposed any particle not yet discovered under 120 GeV, and suggests a gluino mass might be as low as 500 GeV. Even LEP put a limit on the order of 50 GeV on actual particles, although the scalar mass parameter used to determine particle masses in SUSY could be as low as 12 GeV (see also here for post-LEP limits).
There are abundant varieties of candidates for heavier WIMP-like dark matter particles, and are a few candidates for lighter WIMP-like dark matter particles, but really nothing but a right handed neutrino is well motivated in this mass range, and nothing in any well developed theory explains why some of these experiments should be seeing something with considerable significance that others are excluding with considerable significance.
In addition to the limitations on mass, astronomy also tightly limits the cross sections of interactions for dark matter based on examples like the bullet cluster interaction.
In other words, the data from long range astronomy would suggest that the cross section of interaction for dark matter needs to be 0.5-1.25 cm2 g-1, which takes a bit of a unit conversion to match to the way that the dark matter parameter searches report their data in chart form.
"The cross section for a typical interaction involving a neutrino is 5*10^-44 (E/[1 MeV])^2 cm^2."
Usually, these sorts of conflicts end up being resolved in favor of the no new physics direction after more evidence accumulates or more analysis is conducted.
The contradictory evidence and ever tightening constraints imposed by efforts to directly detect dark matter pose a serious quandry for physics. Gravitationally driven behavior attributed to dark matter is common place in astronomy. It is everywhere and well quantified and described at different scale and in different kinds of systems. But, we are increasingly close to ruling out any candidates for dark matter that could fit the criteria imposed by the observations in astronomy that motivate the search.
Since dark matter candidates are often the main phenomenological predictions of leading beyond the Standard Model physics, a failure to find to directly detect the dark matter candidates that they predict also undermines those beyond the Standard Model theories.
Of course, these searches present all sorts of questions. Why do some searches see something at close to a four sigma level, while others rule out the same thing to similar degrees of certainty?
If we are seeing something, why are we seeing particles at masses that have been pretty definitively ruled out by precision measurements of weak force decays and neutrino searches? There shouldn't be anything, either a fundamental particle or a composite one, between bottom quark mass (between 4 and 5 GeV) and 40 GeV that interacts with the electromagnetic or weak force or is quark or includes a quark or is a Standard Model Higgs Boson. Certainly, nothing in the Standard Model fits. All known baryons and all known mesons are too light, topping out at about 5 GeV, apart from a couple of bottom-bottom quark possibilities, and the bottom-bottom quark mesons would be extremely unstable, making them poor dark matter candidates. (Top quarks at 173 GeV are too heavy in addition to being unstable.)
One could imagine, without stretching the Standard Model too far, right handed neutrinos whose masses are many orders of magnitude heavier than their left handed cousins. Glueballs aren't entirely ruled out, but don't seem like a very good fit either. Ground state glueballs should have much lower masses and even if they might be stable in a ground state, they probably wouldn't be stable at higher mass excited states. They are also predicted to get lighter as they gain momentum. Other exotic mesons are also a poor fit.
There are also good theoretical grounds to think that a graviton, if one exists, has no mass.
Even SUSY particles in most of the less ambitious versions of that theory (including the SUSY Higgs boson), are ruled out in that mass range by collider experiments, although Lubos holds out hope for a photino or bino. Gordon Kane, a strong SUSY supporter, hasn't seriously proposed any particle not yet discovered under 120 GeV, and suggests a gluino mass might be as low as 500 GeV. Even LEP put a limit on the order of 50 GeV on actual particles, although the scalar mass parameter used to determine particle masses in SUSY could be as low as 12 GeV (see also here for post-LEP limits).
There are abundant varieties of candidates for heavier WIMP-like dark matter particles, and are a few candidates for lighter WIMP-like dark matter particles, but really nothing but a right handed neutrino is well motivated in this mass range, and nothing in any well developed theory explains why some of these experiments should be seeing something with considerable significance that others are excluding with considerable significance.
In addition to the limitations on mass, astronomy also tightly limits the cross sections of interactions for dark matter based on examples like the bullet cluster interaction.
We have combined results from new X-ray, optical and lensing observations and our N-body simulations of the merging galaxy cluster 1E 0657-56 in order to derive an upper limit on the self-interaction cross-section of dark matter particles, sigma /m. We give constraints on sigma/m based on two independent methods: from the lack of offset between the total mass peak and galaxy centroid of the subcluster that would arise during the merger due to drag on the subcluster halo from DM particle collisions, and from the lack of a decreased mass-to-light ratio of the subcluster due to scattering of DM particles. From the former, we find sigma/m < 1.25 cm2 g−1, and from the latter, sigma /m < 0.7 cm2 g−1, which includes the uncertainty in the impact parameter of the merger (upper limits are from 68% confidence intervals). Our best constraint is a modest improvement of the previous best constraint from conservative analytic estimates of sigma /m < 1 cm2 g−1 (M04). Furthermore, our limit of sigma/m < 1.25 cm2 g−1 is more robust than the best analytic limit, since this method does not depend on the assumption that the subcluster and main cluster M/L ratios were equal prior to the merger. Previous studies have found that sigma /m ∼ 0.5−5 cm2 g−1 is needed produce the observational effects that self-interacting dark matter has been invoked to explain (e.g., nonpeaked galaxy mass profiles and the underabundance of small halos within larger systems). Our results rule out almost this full range of values, at least under the assumption that is velocity-independent.
In other words, the data from long range astronomy would suggest that the cross section of interaction for dark matter needs to be 0.5-1.25 cm2 g-1, which takes a bit of a unit conversion to match to the way that the dark matter parameter searches report their data in chart form.
"The cross section for a typical interaction involving a neutrino is 5*10^-44 (E/[1 MeV])^2 cm^2."
Usually, these sorts of conflicts end up being resolved in favor of the no new physics direction after more evidence accumulates or more analysis is conducted.
The contradictory evidence and ever tightening constraints imposed by efforts to directly detect dark matter pose a serious quandry for physics. Gravitationally driven behavior attributed to dark matter is common place in astronomy. It is everywhere and well quantified and described at different scale and in different kinds of systems. But, we are increasingly close to ruling out any candidates for dark matter that could fit the criteria imposed by the observations in astronomy that motivate the search.
Since dark matter candidates are often the main phenomenological predictions of leading beyond the Standard Model physics, a failure to find to directly detect the dark matter candidates that they predict also undermines those beyond the Standard Model theories.
Thursday, September 1, 2011
Musing On Potential Fourth Generation Fermion Masses
We can say with certainty that any fourth generation quarks of either the up type or down type, would be heavier than a top quark.
It would also follow that like a top quark these would be too heavy to hadronize and would probably have a top quark like decay dominated by decays to the next lightest quark. A b' decay would be dominated by the b' to t to b channel. A t' decay would be dominated by a t' to b' to t to b channel. It is also fair to assume that the ratio of masses between one kind of undiscovered quark and the next heavier one would be at least a factor of two, with a jump from one generation to the next of the same type being at least a factor of four. Thus, a b' quark by this reasoning would be at least 346 GeV and a t' quark by this reasoning would be at least 692 GeV. Experiments are not so sensitive yet, and these are just minimums. If the top to bottom quark mass ratio is any indication, the b' and t' could easily have masses of several TeV or more. Also, any decay of a t' or b' would like a lot like a high energy top quark decay, differing only by a couple of "invisible" neutrinos and a couple of charged leptons from an ordinary top quark decay, and the charged leptons would most likely have the same tau prime generation and opposite charges making their annihilation before detection in a t' decay a very plausible possibility. A t' decay might be almost indistinguishable from a top quark decay in terms of observable end products; the ratio of missing energy to observable end products might be the only really distinctive signature of this decay.
Realistically, the fourth generation charged lepton ought to be the easiest to detect. Charged particles are much easier to find than electrically neutral ones, and a tau prime ought to be lighter than either at t' or a b'. The current experimental lower limit on a tau prime mass is about 100 GeV, but if the tau prime neutrino is more than half of the W mass, as experimental evidence demands that it must be, it would take a decay with about 150 GeV to unveil a tau prime neutrino and if the mass was a bit more than that, one would need a top quark decay of a very high energy top quark to produce one. Thus, the ratio of tau prime to tau mass is not less than about 65:1, if there is a tau prime. This is within the range of generation to generation mass gaps seen in the particles for which masses are currently known, but at the high end of those ratios, although a very heavy tau prime neutrino could damp that a bit.
It isn't clear to me how much LHC will be able to expand LEP boundaries in charged lepton detection, if at all, and if so, when.
Also worth pondering is the question of whether, even if there are fundamental particles yet to be discovered, if we have discovered all reasonably stable particles (e.g. all fundamental particles or composite particles longer lived than a muon).
The faster than hadronization decay of the top quark and of a hypothetical t' and b' and the lack of hadronization of leptons, also means that even if we haven't discovered every possible generation of fundamental particle, that we may have discovered (or theorized with great certainty even if we have not observed) every possible composite particle (with the possible exception of the glueball, which has been theorized but not directly observed and would have a mass on the order of about 300 GeV).
A new stable particle changes to makeup of the universe greatly and has all sorts of practical applications. For example, a stable sterile neutrino could be a dark matter candidate.
But, a t', b', tau prime, tau prime neutrino, W' or Z' that is at least as emphemeral as a top quark and is only created for that very brief moment in the most unnatural of high energy environments may have almost no relevance other than shedding light on the nature of the deeper theory that underlies the Standard Model thereby allowing for more precise theoretical determination of what are currently experimentally derived constants than is possible now (or explaining the innards of exotic astronomical objects like neutron stars and quasars).
For that matter, while the existence and mass of a neutral scalar Standard Model Higgs boson would have some very important implications for the technical aspects of the Standard Model at high energies, but any light Standard Model Higgs boson that isn't ruled out by experiment already would be ephemeral, and would have have few meaningful consequences for physics applications that I can discern.
We understand that world of particles with an electrical charge with such precision that it is almost unthinkable that there exists an electrically charged stable particle out there that hasn't been discovered. So, it is very unlikely that there is a stable quark or stable charged lepton or stable weak force boson out there that hasn't been discovered, or that there is another carrier boson for the electromagentic force in addition to the photon.
One could imagine a stable particle that lacks an electromagnetic charge that hasn't been discovered. Indeed, there are quite a few plausible hypothetical proposals for particles that fit that description such as a heavy sterile neutrino, right handed neutrinos, the lightest supersymmetric particles, a stable neutral Higgs boson, and the graviton. All of the fermions and massive bosons fitting that description would be dark matter candidates.
We can't rules out a stable particle with color charge (IIRC, however, even glueballs are not stable) but no electromagnetic charge with as much confidence, but also have no real strong theoretical reason to expect that one might be out there.
It would also follow that like a top quark these would be too heavy to hadronize and would probably have a top quark like decay dominated by decays to the next lightest quark. A b' decay would be dominated by the b' to t to b channel. A t' decay would be dominated by a t' to b' to t to b channel. It is also fair to assume that the ratio of masses between one kind of undiscovered quark and the next heavier one would be at least a factor of two, with a jump from one generation to the next of the same type being at least a factor of four. Thus, a b' quark by this reasoning would be at least 346 GeV and a t' quark by this reasoning would be at least 692 GeV. Experiments are not so sensitive yet, and these are just minimums. If the top to bottom quark mass ratio is any indication, the b' and t' could easily have masses of several TeV or more. Also, any decay of a t' or b' would like a lot like a high energy top quark decay, differing only by a couple of "invisible" neutrinos and a couple of charged leptons from an ordinary top quark decay, and the charged leptons would most likely have the same tau prime generation and opposite charges making their annihilation before detection in a t' decay a very plausible possibility. A t' decay might be almost indistinguishable from a top quark decay in terms of observable end products; the ratio of missing energy to observable end products might be the only really distinctive signature of this decay.
Realistically, the fourth generation charged lepton ought to be the easiest to detect. Charged particles are much easier to find than electrically neutral ones, and a tau prime ought to be lighter than either at t' or a b'. The current experimental lower limit on a tau prime mass is about 100 GeV, but if the tau prime neutrino is more than half of the W mass, as experimental evidence demands that it must be, it would take a decay with about 150 GeV to unveil a tau prime neutrino and if the mass was a bit more than that, one would need a top quark decay of a very high energy top quark to produce one. Thus, the ratio of tau prime to tau mass is not less than about 65:1, if there is a tau prime. This is within the range of generation to generation mass gaps seen in the particles for which masses are currently known, but at the high end of those ratios, although a very heavy tau prime neutrino could damp that a bit.
It isn't clear to me how much LHC will be able to expand LEP boundaries in charged lepton detection, if at all, and if so, when.
Also worth pondering is the question of whether, even if there are fundamental particles yet to be discovered, if we have discovered all reasonably stable particles (e.g. all fundamental particles or composite particles longer lived than a muon).
The faster than hadronization decay of the top quark and of a hypothetical t' and b' and the lack of hadronization of leptons, also means that even if we haven't discovered every possible generation of fundamental particle, that we may have discovered (or theorized with great certainty even if we have not observed) every possible composite particle (with the possible exception of the glueball, which has been theorized but not directly observed and would have a mass on the order of about 300 GeV).
A new stable particle changes to makeup of the universe greatly and has all sorts of practical applications. For example, a stable sterile neutrino could be a dark matter candidate.
But, a t', b', tau prime, tau prime neutrino, W' or Z' that is at least as emphemeral as a top quark and is only created for that very brief moment in the most unnatural of high energy environments may have almost no relevance other than shedding light on the nature of the deeper theory that underlies the Standard Model thereby allowing for more precise theoretical determination of what are currently experimentally derived constants than is possible now (or explaining the innards of exotic astronomical objects like neutron stars and quasars).
For that matter, while the existence and mass of a neutral scalar Standard Model Higgs boson would have some very important implications for the technical aspects of the Standard Model at high energies, but any light Standard Model Higgs boson that isn't ruled out by experiment already would be ephemeral, and would have have few meaningful consequences for physics applications that I can discern.
We understand that world of particles with an electrical charge with such precision that it is almost unthinkable that there exists an electrically charged stable particle out there that hasn't been discovered. So, it is very unlikely that there is a stable quark or stable charged lepton or stable weak force boson out there that hasn't been discovered, or that there is another carrier boson for the electromagentic force in addition to the photon.
One could imagine a stable particle that lacks an electromagnetic charge that hasn't been discovered. Indeed, there are quite a few plausible hypothetical proposals for particles that fit that description such as a heavy sterile neutrino, right handed neutrinos, the lightest supersymmetric particles, a stable neutral Higgs boson, and the graviton. All of the fermions and massive bosons fitting that description would be dark matter candidates.
We can't rules out a stable particle with color charge (IIRC, however, even glueballs are not stable) but no electromagnetic charge with as much confidence, but also have no real strong theoretical reason to expect that one might be out there.
To Do: Review Frame Dragging Calculations Around Earth
In Newtonian gravity one can perfectly capture the gravitational effects of a system on any body at any significant distance by treating it as a single mass at the center of gravity of the system as a whole.
In General Relativity, this is not generally true. The distribution of mass within a system, and the motion of component parts within that system, has effects that aren't nearly so easily abstracted.
The brings me to the "to do" item to look into, which is how the frame dragging calculation in the experimental tests linked to in the previous post were calculated. It is much easier to do a GR calculation with an assumption of a sphere of uniform mass density that is rotating about its axis than it is to do the calculations reflecting the reality that the Earth does not have a uniform mass density and that geologists know quite a bit about the mass density at very layers of known depths that differ from the average. In principle, the difference in density between the core, mantle and crust, could impact this calculation. I'd like to look at the calculation that was actually done and do some back of napkin estimates to see if the distribution of matter within the Earth could have a material impact on the bottom line predicted frame dragging effect if a homogeneous mass distribution was used in the actual theoretical prediction.
In General Relativity, this is not generally true. The distribution of mass within a system, and the motion of component parts within that system, has effects that aren't nearly so easily abstracted.
The brings me to the "to do" item to look into, which is how the frame dragging calculation in the experimental tests linked to in the previous post were calculated. It is much easier to do a GR calculation with an assumption of a sphere of uniform mass density that is rotating about its axis than it is to do the calculations reflecting the reality that the Earth does not have a uniform mass density and that geologists know quite a bit about the mass density at very layers of known depths that differ from the average. In principle, the difference in density between the core, mantle and crust, could impact this calculation. I'd like to look at the calculation that was actually done and do some back of napkin estimates to see if the distribution of matter within the Earth could have a material impact on the bottom line predicted frame dragging effect if a homogeneous mass distribution was used in the actual theoretical prediction.
Wednesday, August 31, 2011
The Experimental Precision of Select Standard Model and GR Constants
How accurately have we determined the fundamental constants of the Standard Model? Less accurately than you might expect.
The data from the particle data group as of 2011 sets out the story.
For quark masses, the range of values within the appropriate confidence interval (generally 95%) is as follows (the most likely value is not necessarily in the middle of the range since some confidence intervals are lopsided):
up quark = 1.7-3.1 MeV
down quark = 4.1-5.7 MeV
up/down quark mass ratio = 0.35-0.60
mean up and down quark mass = 3.0-4.8 MeV
strange quark = 80-130 MeV (central value 100 MeV).
strange quark mass/mean up and down quark mass = 22-30
charm quark mass = 1.18-1.34 GeV
bottom quark mass (by MS definition) = 4.13-4.27 GeV
bottom quark mass (by 1S definition) = 4.61-4.85 GeV
top quark mass = 171.4-174.4 GeV
The strong force coupling constant related to interactions of quarks and gluons with each other and used in quantum chromodynamics (QCD) is known to an accuracy of approximately 0.6%, which at the scale of Z boson mass is 0.1184 ± 0.0007, although the range of values reported from a robust variety of methods suggests an actual value of closer to 0.119 +/- 0.001.
The canonical value of gluon mass in theory is zero, but a gluon "mass as large as a few MeV may not be precluded" by experimental data.
The first principles estimate of proton and neutron masses from QCD, for example, from theory and the known constants, is accurate to only within about 5%. Given the limited accuracy with which the constants upon which these estimates are based, however, this is quite impressive.
For fundamental leptons and fundamental bosons and quantum electrodynamics (QED) we have much more accurate estimates, although our absolute neutrino mass estimates are far less certain:
electron 0.510998910 ± 0.000000013 MeV
muon 105.658367 ± 0.000004 MeV
tau 1776.82 ± 0.16 MeV
Koide's formula for charged leptons which states that the square of the sum of the square root of the three lepton masses, divided by the sum of the lepton masses equals 1.5, is similarly precisely established.
electron neutrinos < 2 eV (probably closer to 10^-5 eV) The difference between the electron neutrino and muon neutrino mass is on the order of 10^-5 eV and the difference between teh tau neutrino and electron and muon neutrino masses is on the order of 10^-3 eV. But, both the mixing matrixes and masses of neutrinos are not known with great accuracy.
W = 80.399 ± 0.023 GeV
Z = 91.1876 ± 0.0021 GeV
Z-W = 10.4 ± 1.6 GeV
The fine structure constant, which is the coupling constant of electromagnetism is α = 1/137.035999084(51).
There are additional constants in the Standard Model, of course, principally, the weak force coupling constant, the four parameters necessary to determine the 3x3 unitary CKM matrix (which can be parameterized in more than one equivalent way), and the four parameters necessary to determine the 3x3 unitary PMNS matrix, but those are less familiar. The first two are known with precision similar to that of the other weak force observable, while the PMNS matrix elements related to neutrino oscillation are known to accuracies only within roughly a factor of two for values close to zero (or with an 1-value factor of two for numbers close to 1).
There are experimental constraints on the minimum masses of hypothetical fourth generation particles, higher generation W and Z bosons, Higgs boson masses, and masses of other hypothetical particles under various extensions of the Standard Model and for a variety of interactions and decay modes prohibited by the Standard Model (e.g. leptoquarks and axions), but, these are largely consistent with zero although recent neutrino oscillation data most strongly supports more than three generations of neutrinos. Some of the most theoretically well motivated extensions of the Standard Model (predicting proton decay, neutrinoless double beta decay, magnetic monopoles, etc.) turn out to have some of the most experimentally prohibitive boundaries on their existence.
One of the implications of this is that there is very little freedom experimentally for innovation theoretically in electroweak interactions, but some meaningful freedom experimentally for adjustments to quark masses or even to QCD equations.
By comparison, the uncertainty in the gravitational constant's measurement is about one part per thousand, the uncertainty in the cosmological constant's value is about 3.3%, the experimental uncertainty in the measurement of the geodetic effect of general relativity is about 0.2%, and the experimental uncertainty in the measurement of frame dragging in the vicinity of the Earth is about 19% (all of which are consistent with general relativity's predictions). The geodetic and frame dragging effects are measured in terms of deviation from the Newtonian gravitational prediction.
The speed of light in a vaccum, necessary in both quantum mechanics and general relativity, is known with such precision that we use it to define the length of the meter relative to the length of the second.
It is also worth noting that it is not possible to do any remotely complicated calculations in QCD, or very exact calculations in general relativity with a number of bodies on the order of the number of stars in a typical galaxy given current computational technologies and mathematical methods. These kinds of calculations are possible in simple, stylized systems, but not in systems even remotely approaching the complexity of those seen in real life.
The data from the particle data group as of 2011 sets out the story.
For quark masses, the range of values within the appropriate confidence interval (generally 95%) is as follows (the most likely value is not necessarily in the middle of the range since some confidence intervals are lopsided):
up quark = 1.7-3.1 MeV
down quark = 4.1-5.7 MeV
up/down quark mass ratio = 0.35-0.60
mean up and down quark mass = 3.0-4.8 MeV
strange quark = 80-130 MeV (central value 100 MeV).
strange quark mass/mean up and down quark mass = 22-30
charm quark mass = 1.18-1.34 GeV
bottom quark mass (by MS definition) = 4.13-4.27 GeV
bottom quark mass (by 1S definition) = 4.61-4.85 GeV
top quark mass = 171.4-174.4 GeV
The strong force coupling constant related to interactions of quarks and gluons with each other and used in quantum chromodynamics (QCD) is known to an accuracy of approximately 0.6%, which at the scale of Z boson mass is 0.1184 ± 0.0007, although the range of values reported from a robust variety of methods suggests an actual value of closer to 0.119 +/- 0.001.
The canonical value of gluon mass in theory is zero, but a gluon "mass as large as a few MeV may not be precluded" by experimental data.
The first principles estimate of proton and neutron masses from QCD, for example, from theory and the known constants, is accurate to only within about 5%. Given the limited accuracy with which the constants upon which these estimates are based, however, this is quite impressive.
For fundamental leptons and fundamental bosons and quantum electrodynamics (QED) we have much more accurate estimates, although our absolute neutrino mass estimates are far less certain:
electron 0.510998910 ± 0.000000013 MeV
muon 105.658367 ± 0.000004 MeV
tau 1776.82 ± 0.16 MeV
Koide's formula for charged leptons which states that the square of the sum of the square root of the three lepton masses, divided by the sum of the lepton masses equals 1.5, is similarly precisely established.
electron neutrinos < 2 eV (probably closer to 10^-5 eV) The difference between the electron neutrino and muon neutrino mass is on the order of 10^-5 eV and the difference between teh tau neutrino and electron and muon neutrino masses is on the order of 10^-3 eV. But, both the mixing matrixes and masses of neutrinos are not known with great accuracy.
W = 80.399 ± 0.023 GeV
Z = 91.1876 ± 0.0021 GeV
Z-W = 10.4 ± 1.6 GeV
The fine structure constant, which is the coupling constant of electromagnetism is α = 1/137.035999084(51).
There are additional constants in the Standard Model, of course, principally, the weak force coupling constant, the four parameters necessary to determine the 3x3 unitary CKM matrix (which can be parameterized in more than one equivalent way), and the four parameters necessary to determine the 3x3 unitary PMNS matrix, but those are less familiar. The first two are known with precision similar to that of the other weak force observable, while the PMNS matrix elements related to neutrino oscillation are known to accuracies only within roughly a factor of two for values close to zero (or with an 1-value factor of two for numbers close to 1).
There are experimental constraints on the minimum masses of hypothetical fourth generation particles, higher generation W and Z bosons, Higgs boson masses, and masses of other hypothetical particles under various extensions of the Standard Model and for a variety of interactions and decay modes prohibited by the Standard Model (e.g. leptoquarks and axions), but, these are largely consistent with zero although recent neutrino oscillation data most strongly supports more than three generations of neutrinos. Some of the most theoretically well motivated extensions of the Standard Model (predicting proton decay, neutrinoless double beta decay, magnetic monopoles, etc.) turn out to have some of the most experimentally prohibitive boundaries on their existence.
One of the implications of this is that there is very little freedom experimentally for innovation theoretically in electroweak interactions, but some meaningful freedom experimentally for adjustments to quark masses or even to QCD equations.
By comparison, the uncertainty in the gravitational constant's measurement is about one part per thousand, the uncertainty in the cosmological constant's value is about 3.3%, the experimental uncertainty in the measurement of the geodetic effect of general relativity is about 0.2%, and the experimental uncertainty in the measurement of frame dragging in the vicinity of the Earth is about 19% (all of which are consistent with general relativity's predictions). The geodetic and frame dragging effects are measured in terms of deviation from the Newtonian gravitational prediction.
The speed of light in a vaccum, necessary in both quantum mechanics and general relativity, is known with such precision that we use it to define the length of the meter relative to the length of the second.
It is also worth noting that it is not possible to do any remotely complicated calculations in QCD, or very exact calculations in general relativity with a number of bodies on the order of the number of stars in a typical galaxy given current computational technologies and mathematical methods. These kinds of calculations are possible in simple, stylized systems, but not in systems even remotely approaching the complexity of those seen in real life.
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