3.5 keV X-ray line and R-Parity Conserving Supersymmetry

TL;DR

This paper explores R-parity conserving supersymmetric models that can explain the 3.5 keV X-ray line through decaying dark matter particles like gravitinos, axinos, or neutralinos, and discusses their implications for particle physics and cosmology.

Contribution

It introduces specific supersymmetric scenarios within MSSM and NMSSM frameworks that account for the 3.5 keV line while remaining consistent with current constraints.

Findings

Dark matter gravitino or axino around 7 keV decays producing the X-ray line.

Massless bino contributes to effective neutrino number N_eff.

Scenarios with quasi-degenerate bino-singlino states can generate the observed line.

Abstract

We present some R-parity conserving supersymmetric models which can accommodate the 3.5 keV X-ray line reported in recent spectral studies of the Perseus galaxy cluster and the Andromeda galaxy. Within the Minimal Supersymmetric Standard Model (MSSM) framework, the dark matter (DM) gravitino (or the axino) with mass of around 7 keV decays into a massless neutralino (bino) and a photon with lifetime ~10^{28} sec. The massless bino contributes to the effective number of neutrino species N_eff and future data will test this prediction. In the context of NMSSM, we first consider scenarios where the bino is massless and the singlino mass is around 7 keV. We also consider quasi-degenerate bino-singlino scenarios where the mass scale of DM particles are O(GeV) or larger. In such a scenario we require the mass gap to generate the 3.5 keV line. We comment on the possibility of a 7 keV singlino decaying via R parity violating couplings while all other neutralinos are heavy.