Anomalous X-Ray Galactic signal from 7 keV spin-$3/2$ dark matter decay

Abstract

In order to explain the recently reported peak at $3.55$ keV in the galactic x-ray spectrum, we propose a simple model. In this model, the Standard Model is extended by including a neutral spin-$3/2$ vector-like fermion that transforms like a singlet under SM gauge group. This $7.1$ keV spin-$3/2$ fermion is considered to comprise a portion of the observed dark matter. Its decay into a neutrino and a photon with decay life commensurate with the observed data, fits the relic dark matter density and obeys the astrophysical constraints from the supernova cooling.