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Title: Hidden axion dark matter decaying through mixing with QCD axion and the 3.5 keV X-ray line

Hidden axions may be coupled to the standard model particles through a kinetic or mass mixing with QCD axion. We study a scenario in which a hidden axion constitutes a part of or the whole of dark matter and decays into photons through the mixing, explaining the 3.5 keV X-ray line signal. Interestingly, the required long lifetime of the hidden axion dark matter can be realized for the QCD axion decay constant at an intermediate scale, if the mixing is sufficiently small. In such a two component dark matter scenario, the primordial density perturbations of the hidden axion can be highly non-Gaussian, leading to a possible dispersion in the X-ray line strength from various galaxy clusters and near-by galaxies. We also discuss how the parallel and orthogonal alignment of two axions affects their couplings to gauge fields. In particular, the QCD axion decay constant can be much larger than the actual Peccei-Quinn symmetry breaking.
Authors:
 [1] ; ;  [2]
  1. Theory Center, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)
  2. Department of Physics, Tohoku University, Sendai 980-8578 (Japan)
Publication Date:
OSTI Identifier:
22382098
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2014; Journal Issue: 12; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AXIONS; DECAY; GALAXY CLUSTERS; LIFETIME; MASS; NONLUMINOUS MATTER; PERTURBATION THEORY; QUANTUM CHROMODYNAMICS; SIGNALS; STANDARD MODEL; SYMMETRY BREAKING; X RADIATION