Relaxion fluctuations (self-stopping relaxion) and overview of relaxion stopping mechanisms
Journal of high energy physics 2005(5), 80 (2020). doi:10.1007/JHEP05(2020)080
Structure Formation Limits on Axion-Like Dark Matter
We derive structure formation limits on dark matter (DM) composed of keV-scale axion-like particles (ALPs), produced via freeze-in through the interactions with photons and Standard Model (SM) fermions. We employ Lyman-alpha (Ly-{\alpha}) forest data sets as well as the observed number of Milky Way (MW) subhalos. We compare results obtained using Maxwell-Boltzmann and quantum statistics for describing the SM bath. It should be emphasized that the presence of logarithmic divergences complicates the calculation of the production rate, which can not be parameterized with a simple power law behaviour. The obtained results, in combination with X-ray bounds, exclude the possibility for a photophi…
Probing photophobic axion and relaxion dark matter
We investigate the interplay between early universe cosmology and dark matter direct detection, considering axion models with naturally suppressed couplings to photons. In the context of the cosmological relaxation of the electroweak scale, we focus on a scenario of relaxion dark matter, in which the relaxion field constitutes all the observed dark matter relic density and its allowed mass range is fixed to a few keV by construction. In particular, we show that a relaxion particle with mass mϕ=3.0 keV which couples to electrons with gϕ,e=6.8×10−14 is consistent with the XENON1T excess, while accounting for the observed dark matter and satisfying astro/cosmo probes. This scenario uses the el…