2020/07/11 by M. Millea, Marius Millea, Millea, Marius
Physics and Astronomy · #Astrophysics #Axion #Cosmic microwave background #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #Dark Matter and Cosmic Phenomena #Dark matter #FOS: Physical sciences #Particle physics #Physics #Quantum mechanics #Range (aeronautics) #Scientific Research and Discoveries #astro-ph.CO
paper · pdf · doi:10.48550/arxiv.2007.05659
9 pages, 3 figures, v2 some typos fixed and citations added
openalex publication_date 2020/07/11 · arxiv created 2020/07/15 · arxiv updated 2020/07/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Motivated by a possible ∼ eV-mass solar axion explanation to excess events recently detected by the XENON1T experiment, I revisit and update cosmological constraints on axions in this mass range. I find that of the allowed XENON1T mass window (0.1 - 4.1 eV for DFSZ axions and 46 - 56 eV for KSVZ axions), only 0.1 - 0.35 eV remains viable at 95% confidence given current cosmological probes. If a 0.35 eV DFSZ axion existed, it would be detectable at ∼7σ via two independent physical effects with the next-generation CMB-S4 experiment. Conversely, even a combination of CMB-S4 with future DESI measurements falls just short of guaranteeing a 0.1 eV-mass axion can be detected or ruled out. A future limit of ΔN\rm eff<0.027 could rule out any generic axion-like particle across a wide range of masses as long as the reheating temperature is not too low, or alternatively, a future cosmological detection of such an axion-like particle could become the tightest existing observational lower bound on the reheating temperature.