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

Abstract

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 ∼ (109-1011) GeV for trilinear R-parity violating couplings λ ∼ (10-3-10-1) in order to explain the line signal. Moreover, the right-handed stau is predicted to be light, i.e. ∼ (100) GeV, and thus can be looked for at the LHC. Cosmological aspects of the model are also discussed in this study.