Considering the impact that dark matter particles, if the existed, would have on the rate at which neutron star masses grow (potentially tipping neutron stars into black holes), place quite tight and general boundaries on masses of hypothetical dark matter particles for a fairly broad class of potential dark matter particles that aren't completely "sterile" (i.e. not having any non-gravitational interactions).
For reference purposes, the cross-section of interaction between neutrinos and nucleons (i.e. protons and neutrons) is about σnv = 10^−40 cm^2.
The exclusions in this study for a broad range of dark matter particle masses from 100 MeV (which is less than the mass of a pion, which is the least massive particle containing quarks, or the mass of a muon which is a second generation electron) to 1 TeV (about the mass of six top quarks) requires that dark matter particles have interactions with ordinary baryonic matter that are at least a hundred thousand times weaker than the interactions between neutrinos and ordinary baryonic matter (which is basically the entire WIMP mass range).
The Size Of The Exclusion Range Explained
The only Standard Model particles that can exist outside hadrons (i.e. Standard Model particles that don't have quarks or gluons), which have masses below that mass range are electrons, all three kinds of Standard Model neutrinos, and photons (and free up and down quarks in an extremely high temperature gluon quark plasma which is inconsistent with cold or warm dark matter).
This mass range includes muons, tau leptons, free top quarks (up to five of them), as well as high energy free charm and bottom quarks in a gluon-quark plasma. It comes just barely short of including free strange quarks in a high energy gluon quark plasma, which would still have to have an almost hundred thousand times weaker interaction with ordinary baryonic matter than neutrinos.
All observed hadrons, all predicted hadrons and glueballs, all candidates for "meson molecules" and "baryon molecules" and simple "hadron molecules" with both mesons and baryons bound by residual binding forces are also in that range. Even a hypothetical and unthinkably short lived and improbable top quark meson or baryon or tetraquark or pentaquark would be in that mass range. This mass range even includes all isotopes of all observed or predicted atoms are also in that mass ranges. The mass of the heaviest known element (Tennessine which is element 117) is about 273 GeV, which is less than a third of one TeV.
The only composite particles with a single particle mass in excess of 1 TeV each (1074 atomic mass units) are large molecules (for example, a hydrocarbon with a single chain of 76 carbon atoms), and crystals with many atoms.
The exclusion of the dark matter particle parameter space from neutron star masses is strongest for a 10 GeV dark matter particle. This has about the mass of a carbon atom, or the heaviest observed hadrons, such as a bottomonium meson, or a baryon with two bottom quarks and a light quark. For a 10 GeV dark matter particle, the neutron star data imply that any interactions between this dark matter particle candidate and ordinary baryonic matter are at least a billion times weaker than interactions between neutrinos and ordinary baryonic matter.
The paper and its abstract are as follows:
Neutron stars (NSs) can be used to constrain dark matter (DM) since a NS can transform into a black hole (BH) if it captures sufficient DM particles and exceeds the Chandrasekhar limit. We extend earlier work and for the first time take into account the Galactic motion of individual NSs, which changes the amount of the captured DM by as large as one to two orders of magnitude. We systematically apply the analysis to 414 NSs in the Milky Way, and constrain the DM particle mass and its interaction with nucleon simultaneously. We find that the most stringent bound is placed by a few NSs and the bound becomes stronger after considering the Galactic motion.
The survival of observed NSs already excludes a cross section σnX ≳ 10^−45 cm^2 for DM particles with mass from 100 MeV to 10^3 GeV. Especially for a mass around 10 GeV, the constraint on the cross section is as stringent as σnX ≲ 10^−49 cm^2.
Dicong Liang, Lijing Shao, "Improved bounds on the bosonic dark matter with pulsars in the Milky Way" arXiv:2303.05107 (March 9, 2023).
Leveraging This New Information Into Broader Dark Matter Parameter Space Exclusions
Sterile Dark Matter Doesn't Work
What gives this conclusion extra punch is that we can pretty much rule out, based upon observations of inferred dark matter halo shapes and based upon the tight correlation between inferred dark matter halos and ordinary matter distributions in galaxies, completely sterile dark matter particle candidates.
The exclusion for completely sterile dark matter particle candidates can even be extended down to, for example, of keV mass "warm dark matter" particles.
Sterile dark matter particle candidates which are "thermal freeze out" dark matter candidates below the warm dark matter mass scale in the single digit keV masses are likewise ruled out because this would be "hot dark matter" which is inconsistent with the amount of structure observed in the universe, for example, in galaxies and galaxy clusters.
Simple Self-Interacting But Otherwise Sterile Dark Matter Doesn't Work
It also appears that mere self-interaction between dark matter particles doesn't solve the problems of purely sterile dark matter particles either.
There has to be some kind of interaction between dark matter particles an ordinary baryonic matter to explain the way that dark matter is inferred to be distributed in a dark matter particle paradigm.
Bottom Line
So, on one hand, you actually need dark matter to have some kind of not entirely negligible interaction with ordinary matter to reproduce what we observe.
But, on the other hand, a variety of tests have ruled out any kind of interactions with ordinary matter for a large class of potential dark matter particle candidates.
Decaying Or Meaningfully Annihilating Dark Matter Doesn't Work
Model dependent observational constraints require dark matter particles to be either stable or to have a mean lifetime significantly greater than the age of the universe which is about 13.7 billion years old.
Observational data also largely ruling out dark matter candidates that annihilate with other dark matter particles into any products that can be detected with "telescopes" broadly defined at any meaningful rate - effectively ruling out another kind of self-interacting dark matter.
Gaps In The Efforts To Rule Out Dark Matter Particle Candidates That Are Not Sterile Or Nearly So.
There are still a few gaps in the dark matter parameter space.
Gaps For Heavy Dark Matter Candidates
There is another gap between the 1 TeV mass range and MACHO mass object sized dark matter particle candidates (e.g. with medium sized asteroid mass) that are stable over long time periods.
But all forms of baryonic dark matter are ruled out, and a hypothetical stable exotic hadrons made of ordinary matter such as "quark nuggets" and hexaquarks, are likewise ruled out (because there is no plausible argument that they can't be stable).
The main dark matter candidate in this mass range, primordial black holes (PBHs), which were already ruled out except at asteroid mass due to evaporation via Hawking radiation at the low end and a lack of weak lensing at the high end, have now basically been completely ruled out. This last remaining range of masses where PBHs weren't ruled out have been excluded, for example, by the lack of perturbations in the asteroid belts of the solar system basically ruling out the few corners of parameter space that had remained for PBHs with masses with magnitudes similar to asteroid masses.
This doesn't entirely and rigorously rule out some non-baryonic beyond the Standard Model particle in the more than 1 TeV particle mass range up to asteroid mass. But that approach isn't well motivated.
Gaps For Light Dark Matter Candidates
Today's preprint places a quite general upper bound on non-sterile dark matter that does not have a mass under 100 MeV.
There is also an upper bound on the mass of sterile dark matter particles of anything above 10 keV as recounted in warm dark matter papers.
By comparison, an electron has a mass of 511 keV.
More generally, light dark matter particle candidates have to be non-thermal freeze out dark matter candidates in order to keep the mean velocities of these light dark matter candidates low enough to keep them out of the experimentally excluded "hot dark matter" category.
Another gap does not rule out some kinds of axion like particle (ALP) dark matter candidates or other ultralight dark matter candidates (i.e. far below 1 keV) although the ALP exclusion space is full of tiny rule out zones in its parameter space that don't obviously overlap to form a larger exclusion.
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