2025/11/18 by Badziak, Marcin, Gomułka, Adam, Laletin, Maxim +1 · 2 citations
Computer Science · Physics and Astronomy · #Computational Physics and Python Applications #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Particle physics theoretical and experimental studies
paper · doi:10.48550/arxiv.2511.14864
openalex publication_date 2025/11/18 · openalex created_date 2025/11/23 · openalex updated_date 2026/07/28
We present updated cosmological constraints on axion-lepton interactions based on state-of-the-art computations of the thermal axion abundance. By combining Planck Cosmic Microwave Background (CMB) data with baryon acoustic oscillation (BAO) measurements from DESI DR2, we derive improved limits on both lepton-flavor-conserving (LFC) and lepton-flavor-violating (LFV) axion couplings. Incorporating finite axion mass effects substantially strengthens the bounds for axion masses above 0.1 eV compared to those inferred from the ΔN\rm eff constraint alone. The bounds on the LFC axion-tau coupling and LFV axion couplings to tau and muon or electron are improved by several orders of magnitude and the lower bound on the axion decay constant may exceed 106 and 108 GeV, respectively, for axion masses above 1 eV. Our cosmological constraints on LFC axion couplings to muons and taus and LFV axion couplings to tau and muon or electron are stronger than all other constraints for masses above 0.3 eV. In particular, they are stronger than recent collider constraints from Belle-II on τ→ la decays, where l=e or μ. The collider constraints on μ→ ea decays are weaker than the cosmological constraints for axion masses above 100 eV. Our results are relevant for both the QCD axion and axion-like particles (ALPs).