3.5 keV Galactic Emission Line as a Signal from the Hidden Sector

Understand

An emission line with energy of $E\sim 3.5$ keV has been observed in galaxy clusters by two experiments.

• The emission line is consistent with the decay of a dark matter particle with a mass of $\sim 7$ keV.
• In this work we discuss the possibility that the dark particle responsible for the emission is a real scalar ($\rho$) which arises naturally in a $U(1)_X$ Stueckelberg of MSSM.
• In the MSSM Stueckelberg extension $\rho$ couples only to other scalars carrying a $U(1)_X$ quantum number.