Sterile Dark Matter Particles Are Ruled Out
If the phenomena attributed to "dark matter" (DM) are due to a massive particle, this particle has to have some interactions other than purely gravitational ones.
It must interact with either ordinary matter or with other dark matter particles in some way as a consequence of the fact that halos made up of dark matter particles that interact only via gravity have a particular shape which can be calculated analytically (since it is such a simple theory) called the NFW halo for the scientists who calculated it.
But the shape of dark matter halos implied for a dark matter particle this simple NFW is ruled out by observations of stars in galaxies and galaxy clusters. See, e.g., Mariia Khelashvili, Anton Rudakovskyi, Sabine Hossenfelder, “Dark matter profiles of SPARC galaxies: a challenge to fuzzy dark matter” arXiv:2207.14165 (July 28, 2022); Nicolas Loizeau, Glennys R. Farrar, “Galaxy rotation curves disfavor traditional and self-interacting dark matter halos, preferring a disk component or ad-hoc Einasto function” arXiv 2105:00119 (April 30, 2021); Pengfei Li, Federico Lelli, Stacy McGaugh, James Schombert, “A comprehensive catalog of dark matter halo models for SPARC galaxies” arXiv 2001.10538 (January 28, 2020); Daniel B Thomas, Michael Kopp, Katarina Markovič, "Using large scale structure data and a halo model to constrain Generalised Dark Matter" arXiv:1905.02739 (May 7, 2019 last updated May 4, 2020) https://doi.org/10.1093/mnras/stz2559; Marie Korsaga, et al., “GHASP: an Hα kinematics survey of spiral galaxies – XII. Distribution of luminous and dark matter in spiral and irregular nearby galaxies using Rc-band photometry” (September 17, 2018); Theodorus Maria Nieuwenhuizen “Subjecting dark matter candidates to the cluster test” (October 3, 2017); Lin Wang, Da-Ming Chen, Ran Li “The total density profile of DM halos fitted from strong lensing” (July 31, 2017); James S. Bullock, Michael Boylan-Kolchin, “Small-Scale Challenges to the ΛCDM Paradigm” arXiv 1707.04256 (July 13, 2017, last updated September 2, 2019); Davi C. Rodrigues, Antonino del Popolo, Valerio Marra, Paulo L. C. de Oliveira, "Evidences against cuspy dark matter halos in large galaxies" arXiv:1701.02698 (January 10, 2017, last revised 13 June 13, 2017) (accepted in MINRAS) and P.L. Biermann, H.J. de Vega, N.G. Sanchez, "Highlights and Conclusions of the Chalonge Meudon workshop 2012: warm dark matter galaxy formation in agreement with observations" arXiv:1305.7452 (May 31, 2013 last revised June 26, 2013).
Baryon feedback effects can’t solve this halo shape problem. See Lin Wang, Da-Ming Chen, Ran Li, "Baryon effects on the dark matter halos constrained from strong gravitational lensing" arXiv:1706.03324 (June 11, 2017) (accepted in MINRAS).
But warm dark matter (with particle masses on the 1-10 keV order of magnitude) and self-interacting dark matter models could overcome this constraint.
A stronger conclusion, however, is also true. The insufficiently strong correlation with baryonic matter in collisionless DM models contrary to what is observed, compels the conclusion that any dark matter candidate must have some sort of non-gravitational interactions with ordinary matter. See, e.g., Xuejian Shen, Thejs Brinckmann, David Rapetti, Mark Vogelsberger, Adam Mantz, Jesús Zavala, Steven W. Allen, "X-ray morphology of cluster-mass haloes in self-interacting dark matter" arXiv:2202.00038 (January 31, 2022, last revised November 1, 2022) (accepted by MNRAS); Aidan Zentner, Siddharth Dandavate, Oren Slone, Mariangela Lisanti, “A Critical Assessment of Solutions to the Galaxy Diversity Problem” arXiv:2202.00012 (January 31, 2022); Lorenzo Posti, S. Michael Fall “Dynamical evidence for a morphology-dependent relation between the stellar and halo masses of galaxies” arXiv:2102.11282 (February 22, 2021) (Accepted for publication in A&A); Camila A. Correa, Joop Schaye, "The dependence of the galaxy stellar-to-halo mass relation on galaxy morphology" arXiv:2010.01186 (October 2, 2020) (accepted for publication in MNRAS); Paolo Salucci, Nicola Turini, Chiara Di Paolo, "Paradigms and Scenarios for the Dark Matter Phenomenon" arXiv:2008.04052 (August 10, 2020); Paolo Salucci, “The distribution of dark matter in galaxies” (November 21, 2018) (invited review for The Astronomy and Astrophysics Review); Antonino Del Popolo et al., “Correlations between the Dark Matter and Baryonic Properties of CLASH Galaxy Clusters” (August 6, 2018); Paolo Salucci and Nicola Turini, “Evidences for Collisional Dark Matter In Galaxies?” (July 4, 2017); and Edo van Uitert, et al., “Halo ellipticity of GAMA galaxy groups from KiDS weak lensing” (October 13, 2016). Furthermore, distributions of hydrogen in interstellar space are also inconsistent with a dark matter particle that interacts only via gravity. See Zhixing Li, Hong Guo, Yi Mao, “Theoretical Models of the Atomic Hydrogen Content in Dark Matter Halos” arXiv:2207.10414 (July 21, 2022).
These observations effectively rule out warm dark matter (WDM) and self-interacting dark matter (SIDM) candidates that don't have any non-gravitational interactions with ordinary matter.
WIMPs Are Excluded In A Large Mass Range
As I have noted elsewhere, direct dark matter detection experiments have also ruled out dark matter particles that interact via the full strength weak force as well as gravity for a wide range of masses (roughly 1 GeV to 10 TeV). At some masses, even a weak force interactions 100 million times weaker than the full strength weak force are ruled out.
High energy physics experiments likewise rule out pretty much any conceivable beyond the Standard Model particles that have any interactions with Standard Model particles with masses of about 100 MeV to 100 GeV (and into the 1 TeV scale for many particles). Higgs portal dark matter candidates can't really be ruled out below 100 MeV from high energy physics experiments. But realistically, any other kind of beyond the Standard Model particle that interacts with Standard Model particles are excluded right down to masses comparable to the neutrino masses, the lightest of which are in the ballpark of the one meV or less.
Even where high energy physics phenomenologists have proposed new particles to explain anomalies, like leptoquarks or vector-like leptons or additional Higgs bosons or even the X17 particle proposed to explain some nuclear decay angles, none of these particles would have the right properties to be viable dark matter candidates, with the possible exception of heavy right handed neutrinos that are part of a see-saw mechanism giving rise to neutrino mass.
Sufficient Large Macroscopic DM Is Ruled Out
Primordial black holes (PBHs) and very dim objects made of ordinary matter called MACHOS are also ruled out for reasons previously discussed. Observations in our solar system's asteroid belt have pretty much sealed the door to PBHs not already ruled out by other means, and MACHOS were ruled out decades ago.
Thermal Freeze Out DM Is Ruled Out
Beyond the Standard Model particles with a feeble fifth force interaction with ordinary matter (and perhaps other dark matter particles) and a mass more than 10 TeV but smaller than an asteroid are less rigorously ruled out, although they would have too low of a mean velocity to fit the current amount of structure in the universe in a thermal freeze out dark matter scenario.
Thermal freeze out dark matter below the keV mass warm dark matter scale is also ruled out by the current amount of structure in the universe.
So, it is fair to say that thermal freeze out dark matter is pretty much ruled out as well.
Strong Force Bound Dark Matter Is Disfavored
Some proposals have been made for stable strong force bound hadrons other than protons as dark matter candidates, but the lack of evidence of them in high energy physics experiments, among other considerations, strongly disfavors this hypothesis.
Ultralight DM Is Less Tightly Constrained
A variety of ultralight dark matter candidates with masses below the lightest neutrino mass (i.e. sub-meV) are not as rigorously excluded, although as noted above, they must have some fifth force interaction with ordinary matter. Axion-like particles (ALPs) are the main candidate in this mass range.
Axions were originally proposed to address the absence of CP violation in strong force interactions, which was a non-problem to start with, however, and there is no observational evidence for the existence of axions to date.
This is true even though many ALP models propose that they ought to be detectible in laboratory scale experiments that are much less ambitious than particle colliders like Tevatron and the Large Hadron Collider.
DM Ought To Be Simple
The fact that some very simple models that either modify gravity or purport to recognize General Relativity effects not previously understood to be important in galaxy sized or larger systems, can explain a very broad range of phenomena attributed to dark matter, even if they are actually simply operationalizing dark matter particle behavior, also counsel against an unduly Byzantine (i.e. overcomplicated) dark matter sector.
if by 2023, the X17 particle is verified what does this means that for dark matter vs. MOND ?
ReplyDelete@neo
ReplyDeleteThe X17 particle, if it were verified, would have no discernible impact on any dark matter theories or on any modified gravity theories or GR gravity effect hypotheses.
It isn't a dark matter candidate because the proposed particle isn't stable and would have only a tiny fraction of a second lifetime and because it is hypothesized to be produced in baryonic atoms and it is only produced when radioactive isotopes of atoms decay (which involve a tiny percentage of all baryonic matter at any one time).
The average amount of mass from X17 particles at any one time in the vicinity of a given galaxy would have to be many times the total baryonic mass of the galaxy, which instead, this would be about 2% of the mass of the radioactive elements in a galaxy further reduced by the percentage of baryonic mass in a galaxy that is radioactive at any one time (not more than two parts part per ten thousand at a minimum), and further reduced by its lifetime divided by the mean lifetime of the radioactive elements that produce it. A free neutron with a mean lifetime of about 1000 seconds would be the predominant radioactive element in a galaxy while the mean lifetime of an X17 boson would certainly be less than the mean lifetime of a muon which is 10^-6 seconds or so. So, the total mass of X17 bosons at any one time would be at least 10^14 times smaller than the baryonic mass of a galaxy if its existence was proven, which is such a slight deviation from no dark matter that it couldn't be detected with existing observations.
Also, since it would have a short range, it couldn't have the distribution within a DM halo necessary for a dark matter hypothesis to explain what is observed (which requires dark matter to have a halo distribution several times as large as the galaxy it surrounds itself). It would need a range on the order of astronomical units (i.e. the average distance from the Sun to the Earth) plus or minus an order of magnitude at least, and probably more.
But, as a Yukawa force carrying boson, the X17 would have a range of about 4.8 times the proton radius. See http://hyperphysics.phy-astr.gsu.edu/hbase/Forces/exchg.html#c3
For comparison purposes, the weak force has a range of about 0.001 times the proton radius. Interactions with the Higgs boson have a range of 0.006 times the proton radius. And, the nuclear binding force between protons and neutrons in an atomic nucleus (primarily carried by 135 MeV pions) has a range of about 0.6 times the proton radius.
Gluons hypothetically also have zero rest mass, but because of strong force confinement below the quark gluon plasma (QGP) temperature of about 1 GeV (about 10^13 degrees Kelvin), the strong force has an effective range about equal to 2 times the proton radius (and crosses this space at the speed of light).
So, none of these forces or hypothetical forces has any meaningful long range effects.
If the X17 had a coupling constant to baryonic matter comparable to that of the weak force, its would have a greater cross-section of interaction than a hypothetical fermionic WIMP interacting via the weak force of the same mass, so it would be easier for direct dark matter detection experiments to see, even though an X17 would actually be background and not dark matter for such an experiment.
The hypothetical X17 was proposed solely to explain the anomalous angles of radioactive decay products of unstable atomic nuclei (e.g. anti-neutrinos, electrons, photons, and alpha particles) relative to each other that a single group of scientists observers which wasn't seen by other scientists doing comparable experiments that should have revealed it (which could also be explained by flaws in the nuclear structure model of the scientists who claim to have observed it).
In core theory, gravity and the electromagnetic force with force carrying bosons that have zero rest mass (the hypothetical graviton and the photon) have infinite range and are the only long range forces.
i was thinking about this
ReplyDelete“X17 could be a particle, which connects our visible world with the dark matter,” he said in an email.
Jonathan Feng, a professor of physics and astronomy at the University of California at Irvine told CNN he’s been following the Hungarian team’s work for years, and believes its research is shaping up to be a game changer.
If these results can be replicated, “this would be a no-brainer Nobel Prize,” he said.
And Feng said his own team was comparing the Hungarian experiments “with every other experiment that’s been done in the history of physics.”
The only way to explain X17 was a hitherto undetected “fifth force.”
Feng says that, barring experimental error, there was only a one-in-a-trillion chance that the results were caused by anything other than the X17 particle, and this new fifth force.
He added that if another research group could repeat these results with a third type of atom in addition to beryllium and helium, “that would blow the cover off this thing.”
Experimental research groups have already been contacting him, hungry to do that.
More sightings of the fifth force could lead to scientists settling on a specific name for it, understanding its workings more deeply, and developing practical applications for how to harness its power.
They’re leading us closer to what’s considered the Holy Grail in physics, which Albert Einstein had pursued but never achieved. Physicists hope to create a “unified field theory,” which would coherently explain all cosmic forces from the formation of galaxies down to the quirks of quarks.
But the universe isn’t giving up its secrets easily.
“There’s no reason to stop at the fifth,” Feng said. “There could be a sixth, seventh, and eighth force.”
https://www.cnn.com/2019/11/22/world/fifth-force-of-nature-scn-trnd/index.html
Jonathan Lee Feng
Distinguished Professor of Physics & Astronomy
jlf@uci.edu
(949) 824-9821
3162 Frederick Reines Hall
Research Area:
Particle Physics
Education:
Ph.D., Stanford University
Jonathan Feng works at the interface of particle physics and cosmology with the goal of elucidating deep connections between our understanding of the Universe at the smallest and largest length scales. In recent years, the fields of cosmology and particle physics have become increasingly interconnected. er physics, cosmic rays,
Feng holds degrees in physics and mathematics from Harvard, Cambridge, and Stanford universities. He joined the UC Irvine faculty in 2001 and was appointed Professor and Chancellor's Fellow in 2006. His work has been recognized by several awards, including the NSF CAREER Award, UCI's
https://www.physics.uci.edu/people/jonathan-lee-feng
---
Jonathan Lee Feng and Irvine faculty personally reviewed the original data and think it's solid
And Feng said his own team was comparing the Hungarian experiments “with every other experiment that’s been done in the history of physics.”
The only way to explain X17 was a hitherto undetected “fifth force.”
Feng says that, barring experimental error, there was only a one-in-a-trillion chance that the results were caused by anything other than the X17 particle, and this new fifth force.
“There’s no reason to stop at the fifth,” Feng said. “There could be a sixth, seventh, and eighth force.”
x17 could be part of a dark sector of new particle and forces
x17 might couple to stable dark matter particles and imply more fundamental forces
The problem is probably with the calculation of what the SM predicts in a very messy and complicated system compared to what QCD usually tries to deal with.
ReplyDeleteHas anyone considered the possibility that dark matter might have something like the Pauli exclusion principle? And that a very light dark matter particle may experience some kind of degeneracy pressure?
ReplyDeleteX17 particles might be verified by the end of 2023. if successful candidate in our life time if not maybe we'll never see any BSM
ReplyDelete@Ryan
ReplyDeleteThis is generally true of fermionic dark matter and is not the case in the case of bosonic dark matter. But if the cross-section of interaction is basically zero since it doesn't have non-contact interactions and is effectively a point particle it the effect of degeneracy pressure is negligible.
What if fermionic dark matter self-interacts? (Could gravitons be fermions)
ReplyDeleteFrom what I remember from my astrophysics classes, degeneracy pressure would give a cuspy shape at least.
Q1: Could gravitons be fermions?
ReplyDeleteNo.
Gravitons have to be bosons (i.e. must have integer spin and interact according the boson statistics rather than fermionic statistics).
It has been shown, in principle, that any massless spin-2 boson field which coupled in proportion to mass-energy at the strength implied by Newton's constant should give rise to a force indistinguishable from general relativity in all respects not due to the differences between a classical field theory and a quantum field theory.
A graviton, if it exists, must also have at least spin-2. This is because gravity in general relativity has tensor features which requires at least a spin-2 particle to describe, GR can't be described by a vector which a spin-1 boson could carry, or a scalar, which a spin-0 boson could carry. This is also because for forces carried by spin-1 bosons like charges (i.e. mass-energy in the case of gravity) are repulsive, while for spin-2 like charges are attractive.
Bosons can be massive. See, e.g., W bosons, Z bosons, the Higgs boson, pions, kaons, other massive mesons, and helium.
But, the observational constraints on the possible rest mass of the hypothetical graviton are very strict (less than 1.76 * 10^-23 eV as of 2021 per PDG).
There are qualitative features of who gravity behaves that would strongly disfavor massive gravitons as well, although the barriers are not necessarily entirely insurmountable. See https://en.wikipedia.org/wiki/Massive_gravity
Q2: What if fermionic dark matter self-interacts?
This is self-interacting dark matter (SIDM). SIDM can overcome the problem of the deviation between observed halo shape and the NFW prediction. But, it can't overcome the tight observed link between baryonic matter distributions and inferred DM distributions.
The typical SIDM model has a fermionic DM particle of a given mass that interacts only via gravity and a massive carrier boson for the DM self-interaction, giving rise to a Yukawa gauge interaction force, in which the main moving parts are the fermion DM particle mass, the coupling constant of the self-interaction force, and the carrier boson mass. The coupling constant and carrier boson mass parameter space can be constrained by astronomy observations.
Typical SIDM models suggest carrier boson masses on the order of 100 MeV and coupling constants with a strength of the order of the electromagnetic force. But, fitting the parameters of a SIDM model is as much art as science.
But, some of the tightest constraints on SIDM theories come from systems similar to the Bullet Cluster where diffuse interstellar matter and cores of baryonic matter have offset centroids, which seem to be at odds with SIDM parameters estimated from other kinds of systems designed to address to core-cusp problem. See, e.g., https://arxiv.org/abs/0806.2320 ("We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACSJ0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E0657-56), such systems are ideal laboratories for detecting isolated dark matter, and distinguishing between cold dark matter (CDM) and other scenarios (e.g. self-interacting dark matter, alternative gravity theories). MACSJ0025.4-1222 consists of two merging subclusters of similar richness at z=0.586. We measure the distribution of X-ray emitting gas from Chandra X-ray data and find it to be clearly displaced from the distribution of galaxies. A strong (information from highly distorted arcs) and weak (using weakly distorted background galaxies) gravitational lensing analysis based on Hubble Space Telescope observations and Keck arc spectroscopy confirms that the subclusters have near-equal mass. The total mass distribution in each of the subclusters is clearly offset (at >4 sigma significance) from the peak of the hot X-ray emitting gas (the main baryonic component), but aligned with the distribution of galaxies. We measure the fractions of mass in hot gas (0.09^{+0.07}_{-0.03}) and stars (0.010^{+0.007}_{-0.004}), consistent with those of typical clusters, finding that dark matter is the dominant contributor to the gravitational field. Under the assumption that the sub-clusters experienced a head-on collision in the plane of the sky, we obtain an order-of-magnitude estimate of the dark matter self-interaction cross-section of sigma/m < 4cm^2/g, re-affirming the results from the Bullet Cluster on the collisionless nature of dark matter.")
ReplyDeleteFWIW, while the Bullet cluster and similar systems have been claimed to disprove gravitation based theories, both Deur and Moffat's MOG theories, for example, are able to explain these systems.
Also FWIW, I have a very dim view of the quality of Jonathan Feng's scholarship as illustrated, for example, by his latest preprint claiming (contrary to all sorts of evidence to the contrary) that the WIMP paradigm for DM is alive and well:
ReplyDelete"WIMPs, weakly-interacting massive particles, have been leading candidates for particle dark matter for decades, and they remain a viable and highly motivated possibility.
In these lectures, I describe the basic motivations for WIMPs, beginning with the WIMP miracle and its under-appreciated cousin, the discrete WIMP miracle. I then give an overview of some of the basic features of WIMPs and how to find them. These lectures conclude with some variations on the WIMP theme that have by now become significant topics in their own right and illustrate the richness of the WIMP paradigm."
Jonathan L. Feng, "The WIMP Paradigm: Theme and Variations" https://arxiv.org/abs/2212.02479 (December 5, 2022) (lectures given at the 2021 Les Houches Summer School on Dark Matter).
Thanks for that explanation.
ReplyDeleteIntuitively, I think for SIDM to work, it would need a way of shedding energy energy to condense into these structures, right?
Re: an overly complex dark sector, I don't think a simple dark sector is necessarily simpler than our Standard Model sector.
Like, correct me if I'm wrong here, but our detection methods (including particle accelerators?) are biased towards particles that interact with the electroweak and strong forces, correct? So we're somewhat blind to particles that literally have 0 interaction with those forces?
Is there any reason to not think there is a zoo of particles and forces that don't interact with what we see around us?
"they find a range of 0.5-1.0 cm^2/gram could fit the data . . . It would operate at distances consistent with a Yukawa force mediator boson with a mass of 1-100 MeV. This is about 10^14 times stronger than the interaction strength of particles that interact only via the weak force with a Z boson carrier boson (which is 10^25 times stronger than gravity), and is in the same general ballpark of strength as the electromagnetic force and strong force (which is about 100 times stronger than the electromagnetic force)."
ReplyDeleteReferencing the papers cited in this post: https://dispatchesfromturtleisland.blogspot.com/2022/02/simple-dark-matter-models-dont-work.html
"our detection methods (including particle accelerators?) are biased towards particles that interact with the electroweak and strong forces, correct? So we're somewhat blind to particles that literally have 0 interaction with those forces? Is there any reason to not think there is a zoo of particles and forces that don't interact with what we see around us?"
ReplyDeleteParticle accelerators are quite sensitive to the weak force as well. The LHC measures the mass of the W boson that carries the weak force with four significant digit precision and a lot of heavy hadron behavior is weak force driven. The LEP collider measured the Z boson mass to even greater precision (the Z boson also carries the weak force).
Direct detection experiments (like LUX) also rule out WIMP mass DM particles that interact via the weak force.
Your intuition that particle accelerators are blind to particles that interact only via gravity and a DM to DM only fifth force is correct, however.
A very light DM candidate (less than than 105 MeV mass of the muon or so), could also have a Higgs boson interaction (this would be called Higgs Portal Dark Matter). The backgrounds in LHC attempts to measure the decays of the SM Higgs boson are too large and the signal (which is a function of particle rest mass, spin, and QCD color charge) is too small to make significant detections of light BSM particles that get their masses via the Higgs mechanism. Any particle with a standard interaction with the SM Higgs boson in the GeV mass range or up would have thrown off what we see so far, however.
Bounds from the lack of significant missing traverse momentum in collider experiments also significantly limit BSM particles with even quite slight SM particle interactions in the several MeV to several TeV mass range in a very general way.
But, what you get when you limit DM to particles that lack EM, strong, or weak interactions with SM particles is the problem that some non-gravitational interaction with SM particles via these force or a novel fifth force (that might show up in direct detection or particle accelerator experiments if it existed) is necessary because there is such a tight correlation between baryonic matter distributions and ordinary matter distributions. This force must be some SM or non-SM interaction much stronger than gravity that arises between DM particles and SM particles.
This constraint is the other prong of the vice squeezing the parameter space of viable DM candidates.
"But, what you get when you limit DM to particles that lack EM, strong, or weak interactions with SM particles is the problem that some non-gravitational interaction with SM particles via these force or a novel fifth force (that might show up in direct detection or particle accelerator experiments if it existed) is necessary because there is such a tight correlation between baryonic matter distributions and ordinary matter distributions. This force must be some SM or non-SM interaction much stronger than gravity that arises between DM particles and SM particles."
ReplyDeleteI think that's only a problem if gravitational interactions between DM and SM are inelastic. I'm not sure that's actually a problem if these interactions are occurring within a degenerate object?
I see I'm not the first to ask these questions though:
https://scholar.google.ca/scholar?hl=en&as_sdt=0%2C5&q=degenerate+dark+matter&btnG=