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arXiv · 1707.02077

Colder Freeze-in Axinos Decaying into Photons

Kyu Jung Bae·Ayuki Kamada·Seng Pei Liew·Keisuke Yanagi
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Abstract

We point out that 7 keV axino dark matter (DM) in the R-parity violating (RPV) supersymmetric (SUSY) Dine-Fischler-Srednicki-Zhitnitsky model can simultaneously reproduce the 3.5keV X-ray excess, and evade stringent constraints from the Ly-alpha forest data. Peccei-Quinn symmetry breaking naturally generates both axino interactions with minimal SUSY standard model particles and RPV interactions. The RPV interaction introduces an axino-neutrino mixing and provides axino DM as a variant of sterile neutrino DM, whose decay into a monochromatic photon can be detected by X-ray observations. Axinos, on the other hand, are produced by freeze-in processes of thermal particles in addition to the Dodelson-Widrow mechanism of sterile neutrinos. The resultant phase space distribution tends to be colder than the Fermi-Dirac distribution. The inherent entropy production from late-time saxion decay makes axinos even colder. The linear matter power spectrum satisfies even the latest and strongest constraints from the Ly-alpha forest data.

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Kyu Jung Bae, Ayuki Kamada, Seng Pei Liew, Keisuke Yanagi. 2017-07-07. Colder Freeze-in Axinos Decaying into Photons. https://doi.org/10.1103/physrevd.97.055019

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