How Did The Munda Get From Southeast Asia To India And From Where?

On the basis of historical linguistic and language geographic evidence, the authors advance the novel hypothesis that the Munda languages originated on the east coast of India after their Austroasiatic precursor arrived via a maritime route from Southeast Asia, 3,500 to 4,000 years ago. Based on the linguistic evidence, we argue that pre-Proto-Munda arose in Mainland Southeast Asia after the spread of rice agriculture in the late Neolithic period, sometime after 4,500 years ago. A small Austroasiatic population then brought pre-Proto-Munda by means of a maritime route across the Bay of Bengal to the Mahanadi Delta region – an important hub location for maritime trade in historic and pre-historic times. The interaction with a local South Asian population gave rise to proto-Munda and the Munda branch of Austroasiatic. The Maritime Hypothesis accounts for the linguistic evidence better than other scenarios such as an Indian origin of Austroasiatic or a migration from Southeast Asia through the Brahmaputra basin. The available evidence from archaeology and genetics further supports the hypothesis of a small founder population of Austroasiatic speakers arriving in Odisha from Southeast Asia before the Aryan conquest in the Iron-Age.

Felix Rau and Paul Sidwell, "The Munda Maritime Hypothesis" (2019).

Razib Khan has helpful commentary. He notes genetic evidence disfavoring the conventional wisdom that the Munda arrived further north in India by land. In part that is because we normally think of the Austroasiatic people (the most famous Austroasiatic language today is Vietnamese), as land oriented farmers, in contrast to the maritime oriented Austronesians (derived from Taiwan and the settlers of many of the islands in the Pacific Ocean, New Zealand, and island Southeast Asia, as well as Madagascar). He also adds that:

One of the possibilities suggested is a relation to the Aslian subgroup of Austro-Asiatic languages in central Malaysia. This could actually help explain the enrichment for AASI in the Munda: the indigenous Negritos of Malaysia are similar to the people of the Andaman islands! 

Remember, the arrival of Austro-Asiatic farmers in northern Vietnam dates to ~4,000 years ago. The Munda could be relative latecomers to South Asia…

I agree that the hypothesis is a plausible one, and represents yet another extreme localization of the remote origins of a language or language family akin to the likely pin point origins of the proto-Austronesians (to a subregion and indigenous tribe of the island of Formosa), the Austronesian settlers of Madagascar (from a specific part of the island of Borneo where a specific dialect is spoken), the Bantu people (from a county sized area on the Nigerian coast), and in my opinion, also the Chadic languages (from a county sized area of modern day Moldova).

Did Prehistoric South Asians Build A Thirty Mile Long Stone Bridge To Sri Lanka?

A Science Channel TV episode of "What on Earth?" explores the possibility that large stone slabs placed along a sand bar or shoal between India and Sri Lanka (now mostly submerged in shallow water but obvious in a satellite image) were part of a man made bridge that was passable at least some of the year at the time, that is alluded to in the legendary history of the Dravidian people. 

One of the Hindu epics states that the god Rama connected the two with a "magic bridge" (as the producers of the episode interpret it) a.k.a. Adam's Bridge a.k.a. Rama's Bridge a.k.a. Rama Setu. Per that Wikipedia link:

Adam's Bridge (ātām pālam; Sinhala: adamgay palama), also known as Rama's Bridge or Rama Setu (Irāmar pālam, Sanskrit: rāmasetu), is a chain of limestone shoals, between Pamban Island, also known as Rameswaram Island, off the south-eastern coast of Tamil Nadu, India, and Mannar Island, off the north-western coast of Sri Lanka. Geological evidence suggests that this bridge is a former land connection between India and Sri Lanka.

NASA satellite photo: India on top, Sri Lanka at the bottom of the photo

The bridge is 48 km (30 mi) long and separates the Gulf of Mannar (south-west) from the Palk Strait (northeast). Some of the regions are dry and the sea in the area rarely exceeds 1 metre (3 ft) in depth, thus hindering navigation. It was reportedly passable on foot until the 15th century, when storms deepened the channel: temple records seem to say that Adam's Bridge was completely above sea level until it broke in a cyclone in 1480.

The stones are allegedly "from afar" and date to about 5000 BCE and are not natural, while the sand beneath them purportedly dates to 2000 BCE.

The possibility isn't absurd, even though a TV producer can easily make a less than mainstream hypothesis seem more plausible than it would be if all evidence for and against it was considered impartially.

(I tried to embed the video in this post, but couldn't figure out a way to do so using the blogger interface.)

In an example of how India collectively deals with these matters, the Archaeological Survey of India and the government of India informed the Supreme Court of India in a 2007 affidavit that there was no historical proof of the bridge being built by Rama.

Why Is The Universe So Complicated In Ways That Don't Matter?

The Standard Model of Particle physics sets forth a huge range of possible phenomena and interactions. But, most of them are observable only in high energy collider experiments recreating circumstances that have not existed naturally in the near vicinity of Earth or the Sun for many billions of years, certainly, long before life as we know it came into being.

Why do we have such a sophisticated set of parts and rules for such a simple universe that makes so little use of so many of those parts and rules?

There are six kinds of quarks: top, bottom, charm, strange, down and up (in order of mass). But, all ordinary matter made up of quarks is made up of up and down quarks, with an occasional strange quark flitting into and out of existence in a kaon within an atomic nucleus. Gluons and quarks are also always confined within hadrons at temperatures cool enough to come into being on Earth or in the Sun, so we never see them in isolation. There are hundreds of possible mesons and hadrons (even before venturing into tetraquarks, pentaquarks, and hexaquarks), but protons and neutrons and several mesons with no significant strange quark or heavy quark components (i.e. the pion, the omega meson, the rho meson and the sigma meson) that are involved in the nuclear force, suffice to describe almost everything in the observable world to a high degree of accuracy.

Apart from nuclear physics, which only has a narrow range of engineering and scientific applications (apart from understanding fundamental physics for fundamental physics' sake), we don't need to know anything about the strong and weak nuclear forces at all, beyond the fact that nuclei hold together in the absence nuclear fission, nuclear fusion and radioactive decay which could be described with far simpler phenomenological models (and as a practical matter are dealt with that way, even today, in most engineering applications). Nuclear weapons, nuclear fission reactors and the early forms of nuclear medicine were invented as practical applications of nuclear physics before QCD or electroweak theory had reached their modern Standard Model form.

We know that there are three kinds of neutrinos, and three kinds of anti-neutrinos, and some of the rather mysterious properties like neutrino oscillation, but they interact so weakly that there aren't many applications in which knowledge of them is helpful, and there are even fewer applications in which it is necessary, possible and helpful to distinguish between neutrino flavors.

We know that there are two kinds of particles (muons and tau leptons) that are just like electrons but more massive, and how they behave, and we even use muons in a number of practical applications.

But, in a universe with twelve kinds of fundamental fermions, most of what we observe can be understood with just three of them (up quarks, down quarks and electrons), throwing in the electron neutrinos, muon neutrinos and muons and bringing the total to six, for the truly sophisticated. A world without second and third generation fermions at all would be almost impossible for a casual observer to distinguish from our own.

We live in a universe with twelve or thirteen kinds of fundamental fermions, but the eight kinds of gluons are always confined, the Z boson has negligible relevance practically, the W+ and W- boson can be summed up in a black box theory of weak force decay for most practical purposes, and the photon and possibly the hypothetical graviton, are all that we need to deal with for most purposes.

One needs to understand special relativity for many practical purposes, but the far more mathematically and conceptually difficult general relativity for far fewer. We need to understand quantum electrodynamics for many practical applications, but electroweak theory and quantum chromodynamics, for only a very few applications.

We know all of the fundamental physics that will ever be necessary to understand chemistry and biology and geology from first principles.

We understand the least about gravity, but fortunately, while knowing more about it is important in terms of cosmology, and explaining what astronomers see in the very distant depths of the universe, none of the mysteries of dark matter and dark energy have any practical relevance to a species that may never settle more than a handful of nearby star systems, a scale too small for either of those phenomena to have any real relevance. For all but the highest precision applications, even in the solar system and its nearby neighboring star systems, plain old Newtonian gravity and special relativity are quite sufficient to meet our needs.

And, I think that we will probably master the main problems of quantum gravity, dark matter and dark energy, if not in my lifetime (not an unlikely possibility if I live to a ripe old age), in the lifetime of my children or grandchildren (assuming that I will have any). Knowing this won't have many applications, but it will be satisfying and I suspect it will overhaul a lot of mainstream astrophysics related to conventional wisdom about cosmological inflation, the early universe, dark matter and dark energy, in a way that may leave some philosophical ripples that escape into the larger culture.

Cracking the unsolved problems of high energy physics is something we crave, and we might someday discover a layer beneath what we know now that explains Standard Model physics in terms of something simpler at a more microscopic level that unifies it and provides a means from which its many arbitrary constants can be derived from first principles. But, it increasingly looks as if there is no beyond the Standard Model physics that would make differing predictions from the Standard Model in any way that matters.

I am skeptical that we will penetrate that deeper level any time in the next several centuries, no matter how many billions of dollars of resources we throw at it, and I am even more skeptical that we will be able to find any technological applications for it if we do. Understanding the deeper underpinnings of the Standard Model, or at least some of them, will probably only satisfy our intellectual curiosity and make our knowledge of a few physical constants that could then be calculated from first principles. a few orders of magnitude more precise that what we measured experimentally something that is already quite precise in most cases.

Really the only bright spots in terms of progress for the next few centuries in Standard Model physics are an improved understanding of neutrinos, increasingly accurately measured fundamental physical constants, and an increased ability to apply QCD to high energy physics experiments, neutron star properties and the Big Bang.

Much of what we know already is only applicable to the early moments of the universe right after the Big Bang and has little application once nucleosynthesis has run its course.

While we have not yet reached the point of complete scientific knowledge, our understanding of fundamental physics is such that we already know almost everything that could have a technological application that would be economically useful in any way.

We know such more beyond what is economically or technologically useful already, and yet, this knowledge is already esoteric to a great extent.

Now, this doesn't mean that just because we know all of the fundamental rules of physics that we need to use, all of the laws of nature that matter to us, that there isn't lots of critical and economically valuable science to be done, explaining all of the implications of those fundamental rules that are relevant to our complicated world. In areas like condensed matter physics, nuclear engineering, genetics and medicine, there is much to be learned. But, you can go a long way towards doing that with QED and practical simplifications of those fundamental rules for circumstances were they need to be applied and experimental measurements more precise than those that could be derived from first principles.

Why There Are Probably No "True" Hexaquarks That Are Stable In An Unbound State

A "true" hexaquark is a hadron with no substructure with all quarks bound directly to each other via gluons. This is theoretically much easier to realize in forms that according to theory should be extremely unstable than in a stable form.

A deuteron, in contrast, is not a "true" hexaquark, it is a "hadron molecule" made up of two hadrons (a proton and a neutron), with the quarks within the proton and neutron, respectively, bound directly to each other via gluons, and the nucleons themselves, bound to each other through nuclear binding forces mediated by mesons, mostly pions and additionally far fewer kaons and other mesons (often virtual), in a "spillover" of the strong force between quarks in a hadron. (The term "hadron molecule" is something of a "false friend" in terms of terminology, as it is more analogous to an atomic nucleus than what chemists call a molecule.)

We can observe in a deuteron interactions indicative of clustering within its nucleus of a proton and a neutron that are separate structures, rather than of one unitary composite particle made of six quarks.

One of the challenges of QCD experimenters is two distinguish between "true" tetraquarks, pentaquarks, and hexaquarks that are truly quarks bound directly to each other by gluons, and "exotic" hadron "molecules" that are bound to each other either in the manner of protons and neutrons being bound to each other in a nucleus, or via electromagnetism in the manner of the forces that bind atoms to each other.

Distinguishing the three different ways that system of more than three quarks can be bound to each other is subtle and tricky because both "true" tetra-, penta-, hexa-quarks, and hadron molecules bound by mesons to each other with the same valence quark content, are both (1) very short lived, (2) few in number because they have to be created artificially in collider type contexts, and (3) have similar decay products but with different frequencies, polarities and kinematics.

It also doesn't help that the math necessary to predict what the decay products of each scenario looks like is cumbersome and never accurate to much more than the percent level since the underlying physical constants like the strong force coupling constant isn't know very precisely.

But of all the other possible hexaquarks how many are stable?

This is an area of active investigation that is in its infancy. Almost all possible cases are unknown. We are still struggling to determine the underlying structure and nature of lots of X, Y, Z resonances, with most such resonances having multiple plausible explanations. Some of them may be hexaquarks, most of them are probably not. Lots of hexaquark resonances that are naively possible given what we known about QCD at a qualitative level, have never been observed.

We are very confident that in high energy physics interactions simple two valence quark mesons and three valence quark baryons are vastly more likely to be produced than hadrons with more valence quarks than three, although honestly, we're not entirely sure why that is the case beyond some vague heuristic arguments.

We are less confident, but still quite confident, that there are no "true" tetraquarks, pentaquarks or hexaquarks that are stable in an unbound state. The reasoning for this is a mix of the state of what we have studied and observed and our theoretical understanding of the Standard Model. An outline of the reasons for this runs roughly as follows.

If there were, there would be lots of them (because stable particles accumulate). And, we haven't observed them. So, unless they only interact very weakly with everything else (in which case they could make up dark matter), they probably don't exist.

There is certainly no way would could miss large numbers of charged stable "true" hexaquarks given experiments that have been conducted to date, which are highly sensitive to even tiny electrically charged particles, so they would have to be electromagnetically neutral.

This mass would have to show up as missing traverse momentum in collider experiment, since that is what stable exotic, neutral hadrons with few interactions with other matter should look like in a collider because they wouldn't leave decay products and would leave electromagnetic traces within distance from the collision to the collider's instruments which are located by design to catch only quickly decaying hadrons and leptons. And, we haven't seen that in any statistically significant frequency yet.

This mass range isn't one particularly favored for dark matter or for being unobservable in dark matter detection experiments.

A dineutron made up to two neutrons bound by nuclear forces mediated by mesons was first definitively observed in 2012 (see also here) and, as predicted, is was much less stable than a free neutron, decaying in about 10^-22 seconds rather than about 881 seconds for a free neutron. It seems unlikely that a "true" hexaquark with the same valence quarks would be more stable, although one would have to do the calculation (or prove the hypothesis by definitively observing an unstable one of that type, or definitely disprove that hypothesis by definitively observing one was that was stable or metastable) to be sure.

Also, there are no known substances in which strange, charm, or bottom quarks hadrons are stable (due to weak force decay), and there are no cases observed in which top quarks even hadronize (they decay via the weak force faster than the strong force can form a hadron made of them in the vast majority of cases, even though it is theoretically possible in an extreme rare case for an extremely brief time).

So, for a stable hadron with more than three valence quarks, we'd need one make up entirely of up quarks and down quarks as valence quarks that are, in sum, electromagnetically neutral, which confines them to a fairy narrow mass range of approximately 2 GeV/c² plus or minus a fraction of a GeV, and that is a mass range that existing collider experiments have been able to study quite exhaustively.

The other way that you might get a stable "true" hexaquark is in a bound structure that is stable in the same way that a bound neutron is stable, by being bound into a larger structure. This would probably take the interior of a neutron star to create, in which gravitational attraction and Fermi contact force pressure would make up for not quite sufficient standard model binding forces. But, of course, we can't directly observe the interiors of neutron stars and can't externally observe them with sufficient precision to notice the difference yet (although we are improving on that front). Dineutrons (but not "true" hexaquarks) have also been theoretically predicted to exist in at least one isotype of Terbium atoms, although this has not been observed experimentally.

Also, since anything that contains a quark and anti-quark of the same type is prone to annihilation in a short time frame (all forms of quarkonium have short mean lifetimes), that combination of quarks shouldn't be possible in a stable hadron with more than four valence quarks.

Considering all of those limitations, the spectrum of stable "true" hexaquarks, which are stable in an unbound state, if there are any, should be confined to structures with exactly four up quarks and exactly two down quarks (or with exactly four anti-up quarks and exactly two anti-down quarks). This isn't exactly one possibility and it anti-particle, because there are different combinations of spin states that are possible (there are fifteen possible distinguishable spin states for these hexaquarks matched by fifteen possible anti-hexaquark states by my calculation in the ground state, plus theoretically infinitely many unstable excited states). But, the possibilities are still very limited and the mass range of the possible stable "true" hexaquarks is very narrow making it a target that it pretty easy to rule out experimentally.

It is also possible (and indeed likely) that if we run the numbers that this qualitatively possible set of stable "true" hexaquarks aren't actually stable in fact once one does the QCD calculations necessary to determine its properties.

Why is it likely that an allowed stable "true" hexaquark by other measures would not be stable?

A free neutron, which has proportionately the same mix of quarks, is not stable (and is only stable when bound in an atomic nucleus dynamically), although it comes close, and generally speaking, adding more valence quarks to the mix appears to make a hadron less stable rather than more stable.

In particular, a neutron doesn't have to have both of its down quarks in the same spin state, while the hypothetical hexaquark that might be stable would have to have at least some down quarks in the same spin state (two, three or four of them); the up quarks could have mixed spin states which would theoretically be more stable, or the same spin states, which would theoretically be less stable, and hadrons with identical quarks in the same spin state tend to be less stable than those that do not have that property.

Simple Ω baryons with three valence strange quarks, some of which are in same spin state, are an exception to this rule and are more stable than some other particles with mixed spin states with a mean lifetime of about 8*10^-11, but are still unstable. A Δ⁺² baryon and Δ^-1 baryon, made up of three up quarks and three down quarks respectively, are also extremely unstable with mean lifetimes on the order of 10^-24 seconds.

Of the fifteen possible spin states of a hypothetical four down quark and two up quark spin states, the most stable ought to be the one with two down quarks in each possible spin state and one quark quark in each possible spin state, while the other fourteen possible configurations ought to be at least somewhat less stable by comparison. And anti-hexaquarks ought to be just as stable as their ordinary matter counterparts, so you'd only need to examine one possible maximally stable undetected hexaquark state (which should also be the lightest of the fifteen possible hexaquark states) to see if a stable "true" hexaquark that has not yet been detected was possible theoretically within the range of precision in QCD calculations at this point in time.

Another theoretical consideration is that there is no obvious reason that a hexaquark, of the only kind that might be stable considering the factors addressed above, couldn't decay into a pair of neutrons, or into a proton and a Δ^-1 baryon (made of three valence down quarks). So, the hexaquark would have to be lighter than the sum of the masses of its possible decay products with the same quark content, to be stable. But, generally, the more "stuff" a hadron had to overcome to hold itself together, the more massive a hadron is relative to its quark content. So, it seems unlikely that this structure would be lighter than the combined mass of its possible decay products, and hence it is more likely that it would be unstable.

Furthermore, this hexaquark would have to have some means of balancing out the tendency of down quarks to decay to up quarks that is shown in free neutrons, as in the case of a bound neutron, something that is not obviously present in this structure.

In sum, there are very good reasons to expect that there are no "true" hexaquarks that are stable in an unbound state, although there might be extraordinary bound states, such as those arising in the cores of neutron stars, where they might be able to exist in stable form.

Modern Ethiopian Genetics

The rich linguistic, ethnic and cultural diversity of Ethiopia provides an unprecedented opportunity to understand the level to which cultural factors correlate with -- and shape -- genetic structure in human populations. Using primarily novel genetic variation data covering 1,268 Ethiopians representing 68 different ethnic groups, together with information on individuals’ birthplaces, linguistic/religious practices and 31 cultural practices, we disentangle the effects of geographic distance, elevation, and social factors upon shaping the genetic structure of Ethiopians today. 

We provide examples of how social behaviours have directly -- and strongly -- increased genetic differences among present-day peoples. We also show the fluidity of intermixing across linguistic and religious groups. We identify correlations between cultural and genetic patterns that likely indicate a degree of social selection involving recent intermixing among individuals that have certain practices in common. 

In addition to providing insights into the genetic structure and history of Ethiopia, including how they correlate with current linguistic classifications, these results identify the most important cultural and geographic proxies for genetic differentiation and provide a resource for designing sampling protocols for future genetic studies involving Ethiopians.

Saioa López, et al., "The genetic landscape of Ethiopia: diversity, intermixing and the association with culture" bioRXiv (September 5, 2019) doi: https://doi.org/10.1101/756536

(There is excellent background information on Ethiopian history, anthropology and linguistics in the Supplementary Materials).

From the Results section (references omitted; emphasis outside of headings added):

Genetics broadly correlates with linguistic classifications but supports pervasive recent intermixing among ethnic groups speaking diverged languages 

Our study contained individuals from four different branches (second tier of classifications at www.ethnologue.com) within the Afroasiatic (AA) and Nilo-Saharan (NS) language families: the NS Satellite-Core (193 individuals), AA Cushitic (390 individuals), AA Omotic (565 individuals) and AA Semitic (95 individuals) branches. Reflecting a fluidity of genetics across these linguistic classifications, several fineSTRUCTURE-inferred clusters contain individuals from different ethnic groups that represent multiple language categories. For example, the AA Cushitic-speaking Agew cluster genetically with the AA Semitic-speaking Amhara. In addition, the AA Omotic speaking Shinasha, the AA Cushitic-speaking Qimant and the AA Semitic-speaking Beta Israel show very similar inferred ancestry and admixture dates to clusters predominantly containing AA Semitic speakers, with the Qimant and Beta Israel having been reported previously to be related linguistically to the Agew.  

The sample sizes are very impressive for groups like Omotic speakers that are historically undersampled. These are the main correlations. The Amhara language group was probably derived in significant part from language shift from Agew language speakers as do Cushitic Qimant and Beta Israel populations. One Omootic population is close to populations that are now Semitic speaking, also suggesting language shift. Continuing with the results section:

The observed blending of groups’ genetics across language classifications may be attributable in part to ethnic groups adopting their current languages relatively recently and/or to pervasive recent intermixing among distinct Ethiopian groups that reside near one another. To test for the latter, we applied GLOBETROTTER to each of the 78 Ethiopian clusters under the “Ethiopia-internal” analysis, which includes Ethiopians as surrogates for admixing sources and hence can identify intermixing that has occurred among Ethiopian groups. GLOBETROTTER inferred admixture events in 70 clusters in this analysis, 59 (84.3%) of which had estimated dates <30 generations ago (<900 years ago) Across clusters, inferred dates under the “Ethiopia-internal” analysis typically are much more recent than those inferred under the “Ethiopia-external” analysis that does not allow Ethiopian populations as surrogates for the admixing source. This indicates that the “Ethiopia-internal” analysis is identifying recent intermixing among Ethiopian groups rather than relatively older admixture involving non-Ethiopian sources; otherwise dates under the two analyses  would be similar. Supporting the possibility that geographically nearby Ethiopians are intermixing, the GLOBETROTTER “Ethiopia-internal” analysis infers intermixing among Ethiopian clusters that reside more geographically near to each other than expected by chance (p-value < 0.00002).  

Nonetheless, we also explored whether individuals from the same linguistic category are more genetically similar on average, which would reflect a general tendency to share more recent ancestry despite groups changing language and/or some degree of recent intermixing among groups. As an example, on average, individuals from the AA Cushitic, AA Omitic, AA Semitic, and NS classifications, as well as individuals from separate sub-branches within each of these categories, are genetically distinguishable from each other under both the “Ethiopia-internal” and “Ethiopia external” analyses (p-val < 0.01) Indeed, individuals from five of 14 NS-speaking ethnic groups are more genetically similar to the NS-speaking Dinka from Sudan than they are to Ethiopians from AA-speaking ethnic groups, with two of these five (Anuak, Nuer) most genetically similar to the Dinka overall. These observations suggest that the first three tiers of Ethiopian language classifications at www.ethnologue.com are genetically -- in addition to linguistically -- separable on average, and that these genetic differences may not solely be attributable to recent isolation. Consistent with this, individuals from different language categories sometimes display substantially different inferred ancestry. For example, among clusters that predominantly consist of NS speakers, GLOBETROTTER infers admixture events typically occurring <50 generations (<1450 years) ago between EastAfrican/Somali-related sources and SSAfrican-related sources that carry some West/Central African-like ancestry. Markedly different to this, all clusters that predominantly consist of AA Semitic speakers show similar inferred ancestry proportions and admixture events occurring ~57-97 generations (~1600-2800 years) ago between a source related to present-day SSAfricans/Somalians and a source related to present-day Egyptians/W.Eurasians. Meanwhile AA Cushitic and AA Omotic speakers display a wide range of inferred dates and admixture proportions that fall between those inferred for NS and AA Semitic speakers.  

Nilo-Saharan genetic distinctiveness runs very deep, indicating relatively little admixture with Afro-Asiatic language speakers. The Ethio-Semitic speakers, consistent with expectations, so a star-like common ancestry at the expected source date for those languages that have a common source. The divide between Ethio-Semitic speakers and speakers of Afro-Asiatic speakers of non-Ethio-Semitic languages is pre-dates the Ethio-Semitic origin point (as expected), but has more recent common ancestry than the Afro-Asiatic speakers do with the Nilo-Saharan speakers (unsurprising but not as clearly expected). Continuing in the results section:

The Shabo, a hunter-gatherer group and linguistic isolate, show the strongest overall degree of genetic differentiation from other ethnic groups, consistent with the relatively high degree of isolation that has been previously suggested. Under the “Ethiopia-external” analysis, both the Shabo and the AA Omotic-speaking Karo show similar genetic patterns to those of individuals in clusters of predominantly NS speakers near which they both reside. The genetic similarity between the Shabo and NS speakers supports some conclusions based on linguistics  and has been suggested in a study of genetic data from other Shabo individuals. Our analysis finds the Shabo to be significantly most genetically similar to the NS speaking Mezhenger relative to any other ethnic group considered ; for example, merging with the Mezhenger prior to all other NS groups in the fineSTRUCTURE-inferred tree. The Shabo also share very similar inferred admixture events, dated to 300-900 years ago, and ancestry proportions, with the Mezhenger, whom have been suggested to share origins with the Shabo. These inferences are consistent with a high degree of intermarrying among the Shabo and Mezhenger, as has been proposed, and/or Shabo speakers having split from some other NS speakers more recently than 900 years ago, with some degree of current genetic differences between NS speakers and the Shabo attributable to recent isolation (e.g. due to social marginalisation of the Shabo).  

The other group with uncertain linguistic classification in our study, the NegedeWoyto, are significantly differentiable (p-val < 0.001) from all other ethnic groups under the “Ethiopian-internal” analysis, and cluster separately. However, under the “Ethiopia-external” analysis they are not significantly distinguishable from multiple ethnic groups representing all three AA branches and AA Semitic speakers as a whole (p-val > 0.01), consistent with the NegedeWoyto sharing ancestry most recently with AA speakers. Their relatively high amount of Egyptian ancestry (34%) is consistent with the group’s own origin narrative of a migration from Egypt by way of the Abay river. Scholars have also proposed possible genealogical relationships with the Beta Israel and/or Agaw; we observe a high genetic similarity between Negede Woyto and each of these groups though with some degree of recent isolation among them.  

Thus, the ambiguous linguistic classification of two groups is clarified by close genetic ties to the Nilo-Saharan Mezhenger population to the hunter-gather Shabo population in one case (as suspected but shown less clearly from prior investigations) and Egyptian origins consistent with oral traditions for the NegedeWoyto with the other. Continuing in the results section:

Recent intermixing among different groups is associated with shared culture  

For all pairwise combinations of 47 ethnic groups from the SNNPR where we had more detailed cultural information, we also calculated cultural distance as the number of 31 reported cultural practices, primarily related to marriage traditions, that were shared between each pair, with and without weighting by the relative rarity of each practice. In each case, we found a significant association between genetic similarity and reporting of shared cultural traits under the “Ethiopia-internal” analysis (Mantel-test p-value < 0.01), which remained after accounting for geographic or elevation distance (partial Mantel-test p-value < 0.025) or language group (partial Mantel-test p-value < 0.025). This association disappeared under the “Ethiopia-external” analysis, suggesting that ethnicities sharing cultural traits can be ancestrally quite different.  

As an illustration, we find strong genetic similarity -- beyond that explained by spatial distance -- between the Suri, Mursi, and Zilmamo, the only three Ethiopian ethnic groups that share the practice (not included among the 31) of wearing decorative lip plates, in a manner consistent with recent shared ancestry between these three groups and recent isolation from others. Among the 31 cultural traits, six out of the 20 reported by more than one ethnic group exhibited significantly higher (p-value < 0.05) genetic similarity among ethnic groups participating in the practice relative to those who did not participate or whose participation in the practice was unknown. These six cultural traits were male circumcision, female circumcision and four different marriage practices: arrangement by parents, abduction, sororate/cousin, and belt-giving.  

Assuming that individuals have not changed ethnic labels, these findings are consistent with some groups that share cultural practices splitting from one another relatively more recently and/or recently intermixing. To distinguish between these two possibilities, we determined whether two individuals from different groups showed evidence of sharing recent ancestors in a manner consistent with recent genetic exchange between the groups. In particular, only in the scenario where two groups have recently intermixed do we expect some pairings of individuals from the two groups to share a most recent common ancestor (MRCA) for atypically long segments of DNA relative to those shared among all other pairings of individuals from the two groups. Therefore, to test for evidence of recent intermixing between two groups, we assess whether some pairings of individuals, one from each group, have average inferred MRCA segments that are over 2.5 centimorgans (cM) longer than the median length of average inferred MRCA segments across all such pairings of individuals from the two groups. We see such a trend in 134 (12.9%) of 1035 (= 46 choose 2) total pairings of groups considered in this analysis, versus in 11 (20%) of 55 pairings involving male circumcision and 7 (23.8%) of 21 pairings involving Sororate/Cousin marriages. We also see this trend in the AA Cushitic-speaking Dasanech and NS-speaking Nyangatom, who share practices of arranged and abduction marriages. These two groups belong to different language families and show different genetic patterns on average under the “Ethiopia-external” analysis, which is inconsistent with them having recently split. However, they reside near each other, which can be conducive to intermixing and sharing culture, and occasionally cluster together, suggesting some individuals from the two groups are genetically inseparable by our approach. In addition, under the “Ethiopia-internal” analysis, GLOBETROTTER infers reciprocal admixture events 15 generations ago (95% CI: 11-19gen) between the cluster containing the majority of Dasanech (cluster 14) and the cluster containing the majority of Nyangatom (cluster 10). 

Thus, key cultural practices are associated with intermarriage across group lines even for genetically, ethnically and linguistically distinct populations that are geographically close to each other, again, an unsurprising result, but a result that now has more than a conjectural foundation.

Very Subtle Methods In Astronomy

A new paper proposes a new way for astronomers to study gravitational wave causing events, by examining their impact on specific pulsars near events we have already detected.

The gravitational waves travel directly from the event to Earth, but they also travel directly from the event to nearby pulsars. Any effect on the pulsars (basically in the form of a glitch in the pulsar's usual pulse in the electromagnetic spectrum) must then travel from the pulsar to Earth, reaching us several years after we detect the original gravitational wave event.

The fact that we can even aspire to predict and measure something like that is amazing, but the reasoning seems sound and we will be able to determine if the predictions pan out over the next fifteen to fifty years.

Re-visiting gravitational wave events via pulsars

Minati Biswal, Shreyansh S. Dave, Ajit M. Srivastava

(Submitted on 10 Sep 2019)

By now many gravitational wave (GW) signals have been detected by LIGO and Virgo, with the waves reaching earth directly from their respective sources. These waves will also travel to different pulsars and will cause (tiny) transient deformations in the pulsar shape. Some of us have recently shown that the resultant transient change in the pulsar moment of inertia may leave an observable imprint on the pulsar signals as detected on earth, especially at resonance. The pulsars may thus act as remotely stationed Weber gravitational wave detectors. This allows us to revisit the past GW events via pulsars. 

We give here a list of specific pulsars whose future signals will carry the imprints of past GW events, to be specific we constrain it within 50 years. Some interesting cases are, supernova SN1987A with earliest perturbed signals from pulsars J0709-5923 and B0559-57 expected to reach earth in 2023 and 2024 respectively, Crab supernova, with perturbed signal arrival date from pulsar J1856-3754 in 2057, and GW170814 event with its imprints on the signals on the pulsar J0437-4715 reaching earth between 2035-2043. Even the earliest recorded supernova SN185 event may become observable again via pulsar J0900-3144 with the perturbed pulsar signal reaching us sometime between 2033-2066. 

Importantly, even though the strength of the signal will depend on the interior properties of the pulsar, the expected dates of signal arrival are completely model independent, depending only on the locations of the source and the relevant pulsar.

Comments:	5 pages, 1 figure, 2 tables
Subjects:	High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
Cite as:	arXiv:1909.04476 [astro-ph.HE]
	(or arXiv:1909.04476v1 [astro-ph.HE] for this version)

In other astronomy news, some subtle methods of studying gravity, like comparing the general relativistic perihelion of planets with the Newtonian predictions (which, in the case of the planet Mercury, was on the first and most decisive empirical proofs of general relativity) is just very, very difficult to the point of being practically almost impossible for exoplanets.

Relativistic changes to particle trajectories are difficult to detect

Jean-Pierre Eckmann, Farbod Hassani

(Submitted on 10 Sep 2019)

We study the sensitivity of the computed orbits for the Kepler problem, both for continuous space, and discretizations of space. While it is known that energy can be very well preserved with symplectic methods, the semi-major-axis is in general not preserved. We study this spurious shift, as a function of the integration method used, and also as a function of an additional interpolation of forces on a 2-dimensional lattice. This is done for several choices of eccentricities, and semi-major axes. Using these results, we can predict which precisions and lattice constants allow for a detection of the relativistic perihelion advance. Such bounds are important for calculations in N-body simulations, if one wants to meaningfully add these relativistic effects.

Comments:	14 pages, 8 figures
Subjects:	Numerical Analysis (math.NA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); Computational Physics (physics.comp-ph)
Cite as:	arXiv:1909.04652 [math.NA]
	(or arXiv:1909.04652v1 [math.NA] for this version)

The State Of The Muon g-2 Anomaly In A Nutshell

The muon g-2 discrepancy is currently about 3.5 sigma (about two parts per million) by my calculation, based on the data below. New experimental results coming soon will tweak that considerably, although no one knows if it will reduce it or increase it. From the introduction:

The Particle Data Group (PDG) gives an updated value for the muon anomaly in the form [6] 

a exp = 116 592 091(54)(33) × 10^−11. (2) 

The current muon experiment at Fermilab plans to reduce the experimental uncertainty by the factor of four, σfuture ≈ (1.0 ÷ 1.5) × 10^−10 = (10 ÷ 15) × 10^−11 . 

The theoretical results for the muon anomaly in the SM are traditionally represented as a sum of three parts, a SM = a QED + a EW + a had (3) 

with a QED, a EW being the leptonic and electroweak parts, respectively, and a had includes quarks. In fact, the separation in Eq. (3) is such that quark loops are included also in a EW. The leptonic part is computed in perturbation theory and reads a 

QED = 116 584 718.95(0.08) × 10^−11. (4) 

The computation extends up to five-loop level, using both analytical and numerical techniques. At present, the numerical results are steadily being checked/refined with powerful analytical methods for Feynman integral evaluation. In view of the experimental uncertainty, the QED part of the theory prediction for the muon anomaly can be considered to be exact, giving a negligible uncertainty. 

The electroweak part is known to two loops and reads a EW = 153.6(1.0) × 10^−11. (5) 

The absolute value of a EW is small and the uncertainty of this contribution is negligible for comparison with present experiments. The hadronic part a had in the SM is related to quark contributions. To leading order (LO) in the fine structure constant α it is given by the two-point function of hadronic electromagnetic currents through the vacuum polarization of the photon. In order to match the experimental accuracy of the muon anomaly one has to include next-to-leading order (NLO) contributions in α. At this order the four-point function of hadronic electromagnetic currents starts to contribute. 

The accurate calculation of light hadronic contributions is impossible in perturbative Quantum Chromodynamics (QCD) as they are represented by (almost) massless light quarks and are infrared (IR) singular in perturbation theory. This is the main obstacle for obtaining high precision SM predictions. Instead, the theoretical estimates for hadronic modes utilize scattering data. The LO hadronic contribution extracted from e +e − data is given by

a(LO; had; e +e −) = 6931(33)(7) × 10^−11. (6) 

Other estimates may include also data from hadronic τ lepton decays [4], a(LO; had; τ ) = (689.46 ± 3.25) × 10^−10. (7) 

In our estimates we stick to the PDG value in Eq. (6) for definiteness, called a(LO; had). The hadronic contribution is rather large and should be computed with a precision of one or two per mille. This is a challenge for the theory in a situation where there are no appropriate tools for an analytical theoretical computation. Presently, the lattice is emerging as a promising tool for this task. In NLO there are further hadronic contributions. They are extensively discussed in the literature and estimated in various approaches. 

The current total SM prediction reads: 

a SM = 116 591 823(1)(34)(26) × 10^−11. (8) 

The difference ∆aµ = a exp − a SM = 268(63)(43) × 10^−11 (9)  

might uncover physics beyond the SM. It is not formally statistically significant yet but is considered to be rather serious for the prospect of discovering new physics. The main theoretical uncertainties come from the hadronic LO part and from the NLO contribution of the genuine four-point function called light-by-light (LBL).

The paper is here.

The errors in theoretical calculation by component are summarized roughly as follows (in comparable units):

QED 0.08 (i.e. 0.2% of the total)

Weak Force 1.00 (i.e. 2.9% of the total)

QCD 33.73 (i.e. 96.9% of the total).

The error from the components combined is +/-  34 * 10^-11.

The theoretical value also has a +/- 23 * 10^-11 component  and a +/ 1.0 * 10^-11 component. I don't know what they stand for but that brings total theoretical prediction error to +/- 43 * 10^-11.

Proportion of total value from each component:

QED 99,994% (116 584 718.95)

Weak Force 0.00013% (153.6)

QCD 0.006% (6931)

Relative error percentage:

QED 0.000 000 0686%

Weak Force 0.65%

QCD 4.88%

Gravity is not considered but would make a negligible contribution if it was considered.

The error bars on the error are also greatest where the error is greatest.

There are actually two parts of the hadronic component. The larger one, which is more accurately known but still a significant source of error involves hadronic vacuum polarization, the smaller one, which as a 25% margin of error, is the hadronic "light on light" contribution which involves the interactions of light virtual quarks. Broken down the impacts times 10^-11 are about:

HVP           6 850.6 ± 43

HLbL               105 ± 26

Thus, about a third of the total error comes from a component that makes up only about 0.0001% of the total result, and almost all but 3% or so of the remaining error comes from a component that makes up only 0.004% of the total result.

The absolute value of the combined hadronic component has fallen about about 24 * 10^-11, about 0.3%, and the error has fallen from about 50.25 to about 33.73, about a third, since the figures above from a different source that I cite above were reported. I am suspicious, however, that the errors stated in the theoretical value quoted above in the new review article might actually be electro-weak (1), HVP (34) and HLbL (26), even though that is not exactly what the article states, in which the combined QCD error is 43 which is only about a 15% improvement in QCD error from my previous source attributable almost entirely to refinements in the HVP part.

The combined experimental error is +/- 63 * 10^-11, currently about a third greater than the theoretical error. The new Fermi experiment should bring the experimental error down to about +/- 16 * 10^-11.

An experimental value two standard deviation above what was measured would leave a discrepancy of 142 to be explained with improved theoretical estimates. HVP and HLbL minus two standard deviations would be about:

HVP 6764.6 (a reduction of 86 which is about 1.3%).
HLbL 53 (a reduction of 52 which is about 50.5%).

The combined reduction would be 138.

So, realistically, almost all of the muon g-2 anomaly could be explained by a modestly overstated HVP contribution and a greatly overstated HLbL contribution in the QCD part of the theoretical muon g-2 calculation. Indeed, I think it is more fruitful to use the muon g-2 anomaly as a pointer towards what kind of errors appear to be present in the QCD calculations than to use it as a pointer towards new physics.

Of course, unknown unknowns could increase both theoretical and experimental errors.

This issue is discussed another recent review article that I mention in a post on March 26, 2019. The issue is also discussed in previous blog posts on June 29, 2018,  February 1, 2018 (regarding a resolution that turns out to have been obviously flawed upon peer review), January 3, 2018, August 8, 2017, January 13, 2017, November 22, 2013 (humorous), November 21, 2013, and November 12, 2013.

UPDATE September 11, 2019:

A paper from earlier this year lays out the issues well:

Review of Lattice QCD Studies of Hadronic Vacuum Polarization Contribution to Muon g-2

Kohtaroh Miura

(Submitted on 25 Jan 2019 (v1), last revised 4 Jun 2019 (this version, v2))

Lattice QCD (LQCD) studies for the hadron vacuum polarization (HVP) and its contribution to the muon anomalous magnetic moment (muon g-2) are reviewed. There currently exists more than 3-sigma deviations in the muon g-2 between the BNL experiment with 0.5 ppm precision and the Standard Model (SM) predictions, where the latter relies on the QCD dispersion relation for the HVP. The LQCD provides an independent crosscheck of the dispersive approaches and important indications for assessing the SM prediction with measurements at ongoing/forthcoming experiments at Fermilab/J-PARC (0.14/0.1 ppm precision). The LQCD has made significant progress, in particular, in the long distance and finite volume control, continuum extrapolations, and QED and strong isospin breaking (SIB) corrections. In the recently published papers, two LQCD estimates for the HVP muon g-2 are consistent with No New Physics while the other three are not. The tension solely originates to the light-quark connected contributions and indicates some under-estimated systematics in the large distance control. The strange and charm connected contributions as well as the disconnected contributions are consistent among all LQCD groups and determined precisely. The total error is at a few percent level. It is still premature by the LQCD to confirm or infirm the deviation between the experiments and the SM predictions. If the LQCD is combined with the dispersive method, the HVP muon g-2 is predicted with 0.4% uncertainty, which is close upon the target precision required by the Fermilab/J-PARC experiments. Continuous and considerable improvements are work in progress, and there are good prospects that the target precision will get achieved within the next few years.

Comments:	20 pages, 9 figures, Proceedings of LATTICE2018
Subjects:	High Energy Physics - Lattice (hep-lat)
Cite as:	arXiv:1901.09052 [hep-lat]
	(or arXiv:1901.09052v2 [hep-lat] for this version)

 

B Meson Decay Anomalies Getting Smaller With More Data

A global fit to b→cτν¯ anomalies after Moriond 2019

Suman Kumbhakar, Ashutosh Kumar Alok, Dinesh Kumar, S. Uma Sankar

(Submitted on 6 Sep 2019)

At Moriond 2019, Belle collaboration announced their new measurements on RD and RD∗ which are in agreement with their Standard Model (SM) predictions within 1.2σ. After inclusion of these measurements, the discrepancy between the world averages and the SM predictions of RD-RD∗ comes down from 4.1σ to 3.1σ. Here we do a global fit by taking all measurements in b→cτν¯ transition. We find that there are seven allowed new physics solutions, each with different Lorentz structure. Further we show that it is possible to distinguish between them by means of the five observables: the τ polarization fraction in the decay B→Dτν¯, the precision measurement of RD, the forward-backward asymmetries in the decays B→(D,D∗)τν¯ and the branching ratio of Bc→τν¯.

Comments:	5 pages, Based on arXiv:1903.10486, Contribution to proceedings of EPS-HEP 2019, July 10-17, 2019, Ghent, Belgium
Subjects:	High Energy Physics - Phenomenology (hep-ph)
Cite as:	arXiv:1909.02840 [hep-ph]
	(or arXiv:1909.02840v1 [hep-ph] for this version)

Submission history

From: Suman Kumbhakar [view email]
[v1] Fri, 6 Sep 2019 12:02:50 UTC (23 KB)

The abstract in the pre-print version of the earlier paper (1903.10486) upon which this one is based also makes a notable observation missing in the current abstract:

We find that a large number of previously allowed solutions become equivalent to the solution where the new physics operator has (V − A) form. 

"(V-A) form" means a key term in which a vector current is subtracted from an axial current.

Looking more and more like a fluke, although the authors argue that the evidence still points to new physics. The introduction to the earlier article is informative:

The flavor ratios RD(∗) = Γ(B → D(∗) τ ν¯)/Γ(B → D(∗) e/µ ν¯) were measured by BaBar, Belle and LHCb collaborations. The average values of these measurements differ from their respective Standard Model (SM) predictions by 3.9σ. In all these measurements, the τ lepton was not reconstructed but was identified through other kinematical information. LHCb collaboration attempted to reconstruct the τ lepton through its 3π decay mode, in making a seperate measurement of RD∗. Post this measurement, the discrepancy of RD-RD∗ data with SM predictions increased to 4.1σ. The observed values of RD and RD∗ are noticeably higher than their respective SM predictions in all these measurements. These measurements indicate the violation of lepton flavor universality. The higher values of RD and RD∗ are assumed to occur due to new physics (NP) contribution to the b → c τ ν¯ decay. New physics in b → c {e/µ} ν¯ is ruled out by other data. LHCb collaboration also measured the related flavor ratio RJ/ψ = Γ(Bc → J/ψ τ ν¯)/Γ(Bc → J/ψ µ ν¯) and found it to be 1.7σ higher than the SM prediction. In the SM, the charged current transition b → c τ ν¯ occurs at tree level. To account for the measured higher values of flavor ratios, the NP amplitudes are expected to be about 10% of the SM amplitude. The complete list of effective operators leading to b → c τ ν¯ decay are listed in ref. [13]. These operators can be classified by their Lorentz structure. Different Lorentz structures contribute differently to the flavor ratios. The coefficients of these operators are determined by fitting the theoretical predictions to the data. The purely leptonic decay Bc → τ ν¯ is also driven by these operators. This decay mode has not been observed yet but the total decay width of Bc meson has been measured. 

In the SM, the branching ratio for this mode is small because of helicity suppression. The constraint that the branching ratio for Bc → τ ν¯ should be less than 1 leads to useful constraints on a class of NP operators. In addition to the branching ratios, it is possible to measure various other quantities in B → D∗ τν¯ decay. The polarization fractions of the τ lepton (P D∗ τ ) and the D∗ meson (f D∗ L ) are two such quantities which can be measured even without the reconstruction of τ lepton. These observables can lead to discrimination between different NP operators. If the τ lepton is reconstructed and its momentum determined then it is possible to measure two more angular observables, the forward-backward asymmetry AD∗ F B and longitudinal-transverse asymmetry AD∗ LT. If these asymmetries are measured then it can lead to further discrimination between NP operators. 

The new physics can be parametrized in terms of five different operators Oi , with different Lorentz structures. They are 

OVL = (¯cγµPLb)(¯τ γµPLν) , OVR = (¯cγµPRb)(¯τ γµPLν) ,

OSL = (¯cPLb)(¯τPLν), OSR = (¯cPRb)(¯τPLν), OT = (¯cσµνPLb)(¯τσµνPLν). (1) 

In writing the above operators, we assumed that the neutrino is purely a left chiral fermion. These operators appear in the effective Hamiltonian with coefficients C˜ i , where we assume C˜ i are real. First we consider the effect of each individual Oi on RD-RD∗ anomaly. 

• The operator OVL has the same Lorentz structure as the SM operator. This amplitude adds to SM amplitude and hence RD and RD∗ become proportional to (1 + C˜ VL )^2 . A fit to data gives a solution for C˜ VL because the fractional increase in RD and RD∗ are roughly the same. 

• If the NP operator is OVR, RD is proportional to (1 + C˜ VR )^2 where as RD∗ depends to a large extent on (1 − C˜ VR )^2 . Given the data, it is not possible to find a common solution to both RD and RD∗ . 

• The operators OSL and OSR contain the pseudoscalar bilinear ¯cγ5b. Hence the amplitudes due to these operators are not subject to helicity suppression. These amplitudes predict large branching ratios for Bc → τ ν¯. Therefore, the constraint on this branching ratio restricts the solutions given by RD-RD∗ fit. 

• For the solution with the tensor operator OT, the predicion of f D∗ L is much smaller than those of other solutions. Hence an accurate measurement of this polarization fraction can distinguish this solution from others. 

Last year, Belle collaboration announced the first measurement of f D∗ L. This year, at Moriond, Belle collaboration announced a new measurement of RD and RD∗. A novel feature of this measurement is the tagging of the τ lepton in the B → D/D∗ τ ν¯ decays. This latest measurement is consistent with the SM prediction. Inclusion of this measurement in computing a new world average brings down the discrepancy with SM from 4.1σ to 3.1σ. This is still a substantial discrepancy. Moreover, the central values of the new measurement are also higher than the SM predictions. This has been the feature of all RD and RD∗ measurements no matter what the discrepancy is. Given that the measured deviation from the SM prediction is always positive, it is expected that there is indeed new physics present. In this letter, we study the effect of these two recent Belle measurements on various solutions to RD-RD∗ anomaly.

So, Belle's measurements are the ones reducing the size of the anomaly and reducing the number and variety of possible new physics explanations. The fact that the anomaly is restricted to b quark decays to a charm quark and a tau lepton (with the associated tau anti-neutrino), which involve comparatively small data sets, and can be tricker to measure, also casts doubt on the lepton universality violations observed being due to anything more than statistical flukes and systemic experimental errors (and/or theoretical conceptual errors). 

The across the board measurement of values in excess of the Standard Model prediction also points to comparable systemic experimental errors and/or theoretical conceptual errors as a likely source of the apparent discrepancies with the Standard Model (as opposed to new physics, as the authors suggest).