Axino dark matter in light of an anomalous X-ray line

Axino as the superpartner of axion that solves the strong CP problem can be a good candidate of dark matter. Inspired by the 3.5 keV X-ray line signal found to be originated from galaxy clusters and Andromeda galaxy, we study axino models with R-parity violations, and point out that axino dark matter with trilinear R-parity violations is an attractive scenario that reproduces the X-ray line. The Peccei-Quinn scale is required to be fa ∼ O(109−1011) GeV for trilinear R-parity couplings λ ∼ O(10−3 − 10−1) in order to explain the line signal. Moreover, the right-handed stau is predicted to be light, i.e. ∼ O(100) GeV, and thus can be looked for at the LHC. Cosmological aspects of the model are also discussed in this study. ar X i