The Irreducible Axion Background

Abstract

Searches for dark matter decaying into photons constrain its lifetime to be many orders of magnitude larger than the age of the Universe. A corollary statement is that the abundance of any particle that can decay into photons over cosmological timescales is constrained to be much smaller than the cold dark-matter density. We show that an $\text{irreducible}$ freeze-in contribution to the relic density of axions is in violation of that statement in a large portion of the parameter space. This allows us to set stringent constraints on axions in the mass range $100\mathrm{eV}-100\mathrm{MeV}$. At $10\mathrm{keV}$ our constraint on a photophilic axion is $g_{a\gamma \gamma }\lesssim 8.1\times 10^{-14}{\mathrm{GeV}}^{-1}$, almost three orders of magnitude stronger than the bounds established using horizontal branch stars; at $100\mathrm{keV}$ our constraint on a photophobic axion coupled to electrons is $g_{aee}\lesssim 8.0\times 10^{-15}$, almost four orders of magnitude stronger than present results. Although we focus on axions, our argument is more general and can be extended to, for instance, sterile neutrinos.

7+14 pages, 2+9 figures; v2 additional references and updated to the latest INTEGRAL constraints

References in corpus (19)

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• Collider Probes of Axion-Like Particles
• Revised constraints and Belle II sensitivity for visible and invisible axion-like particles
• General Constraints on Dark Matter Decay from the Cosmic Microwave Background
• Cosmological constraints on exotic injection of electromagnetic energy
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• How warm are non-thermal relics? Lyman-$\alpha$ bounds on out-of-equilibrium dark matter
• Axion constraints in non-standard thermal histories
• MeV sterile neutrinos in low reheating temperature cosmological scenarios
• Thermal QCD Axions across Thresholds
• Constraint on the Effective Number of Neutrino Species from the WMAP and SDSS LRG Power Spectra
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Cited by in corpus (40)

• Astrophysical Axion Bounds: The 2024 Edition
• Axion-sourced fireballs from supernovae
• Multimessenger Constraints on Radiatively Decaying Axions from GW170817
• Effective portals to heavy neutral leptons
• Probing the Blue Axion with Cosmic Optical Background Anisotropies
• Axion Astrophysics
• Investigating the gamma-ray burst from decaying MeV-scale axion-like particles produced in supernova explosions
• Superradiant axion clouds around asteroid-mass primordial black holes
• Dark Matter prospects with COSI: ALPs, PBHs and sub-GeV Dark Matter
• Constraining MeV-scale axion-like particles with Fermi-LAT observations of SN 2023ixf
• Detecting Axion Dark Matter with Black Hole Polarimetry
• Detecting Axion-Like Particles with Primordial Black Holes
• Slaying Axion-Like Particles via Gravitational Waves and Primordial Black Holes from Supercooled Phase Transition
• Supernova limits on 'QCD axion-like particles'
• Constraining axion and compact dark matter with interstellar medium heating
• Search for ultralight dark matter in the SuperMAG high-fidelity dataset
• From QFT to Boltzmann: Freeze-in in the presence of oscillating condensates
• Back to the phase space: thermal axion dark radiation via couplings to standard model fermions
• The Minimal Massive Majoron Seesaw Model
• NuSTAR bounds on radiatively decaying particles from M82
• New insights into axion freeze-in
• Searching for relativistic axions in the sky
• Irreducible cosmological backgrounds of a real scalar with a broken symmetry
• New Source for QCD Axion Dark Matter Production: Curvature Induced
• Insights on the Cosmic Origin of Matter from Proton Stability
• Upcoming searches for decaying dark matter with ULTRASAT ultraviolet maps
• Strong Constraints on Dark Photon and Scalar Dark Matter Decay from INTEGRAL and AMS-02 data
• Unlocking Discovery Potential for Decaying Dark Matter and Faint X-ray Sources with XRISM
• Lyman-$\alpha$ limit on axion-like cold dark matter
• Right handed neutrino production from $Z^{\prime }$ interactions in forward search experiments
• Improved cosmological constraints on axion-lepton interactions
• Probing Non-Minimal Dark Sectors via the 21 cm Line at Cosmic Dawn
• Flavor-changing axions and Dirac neutrino masses
• Nucleosynthesis and CMB bounds on photophilic ALPs: a fresh look
• Orbital Dynamics of the Solar Basin
• Translating current ALP photon coupling strength bounds to the Randall-Sundrum model
• The Dark Photon: a 2026 Perspective
• Loop-Level Lepton Flavor Violation and Diphoton Signals in the Minimal Left-Right Symmetric Model
• Beyond thermal approximations: Precise cosmological bounds on Axion-Like Particles
• LHC-friendly freeze-in dark matter via Higgs portal