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Irreducible Axion Background.

Kevin Langhoff1,2, Nadav Joseph Outmezguine1,2, Nicholas L Rodd3

  • 1Berkeley Center for Theoretical Physics, University of California, Berkeley, California 94720, U.S.A.

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|December 23, 2022
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Summary
This summary is machine-generated.

New research reveals that axions, a type of dark matter particle, can violate cosmological constraints. This study establishes strong new limits on axion properties, impacting searches for these elusive particles.

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Area of Science:

  • Cosmology
  • Particle Physics
  • Astrophysics

Background:

  • Searches for decaying dark matter particles, particularly into photons, impose strict limits on their lifetimes and abundances.
  • Previous constraints imply that any particle decaying into photons over cosmological timescales must be significantly less abundant than cold dark matter.

Purpose of the Study:

  • To investigate whether axions, a dark matter candidate, can evade existing cosmological constraints.
  • To derive new, stringent constraints on axion properties within a specific mass range.

Main Methods:

  • Analysis of the irreducible freeze-in contribution to the relic density of axions.
  • Comparison of theoretical predictions with cosmological abundance limits.
  • Derivation of constraints on axion-photon and axion-electron couplings.

Main Results:

  • An irreducible freeze-in mechanism for axions violates established cosmological abundance limits over a significant parameter space.
  • New constraints are placed on axions with masses between 100 eV and 100 MeV.
  • Specific constraints derived for photophilic axions (g_{aγγ}≲8.1×10^{-14} GeV^{-1} at 10 keV) and photophobic axions coupled to electrons (g_{aee}≲8.0×10^{-15} at 100 keV).

Conclusions:

  • The freeze-in production of axions is constrained by cosmological observations.
  • This work provides significantly stronger limits than previous studies using horizontal branch stars and other methods.
  • The methodology can be extended to constrain other particle candidates, such as sterile neutrinos.