http://arxiv.org/abs/1403.0865
The recently reported X-ray line signal at $E_\gamma \simeq 3.5 {\rm keV}$ from a stacked spectrum of various galaxy clusters and Andromeda galaxy may be originated from a decaying dark matter particle of the mass $2 E_\gamma$. A light axion-like scalar is suggested as a natural candidate for dark matter and its production mechanisms are closely examined. We show that the right amount of axion relic density with the preferred parameters, $m_a \simeq 7 {\rm keV}$ and $f_a \simeq 4\times 10^{14} {\rm GeV}$, is naturally obtainable from the decay of inflaton or saxion decay. The small misalignment angles of the axion, $\theta_a\sim 10^{-4} -10^{-1}$, depending on the reheating temperature, can be also the source of axion production. The model satisfies the constraints required for structure formation and iso-curvature perturbation.
H. Lee, S. Park and W. Park
Wed, 5 Mar 14
15/75