Galactic Gamma Ray Excess and Dark Matter Phenomenology in a $U(1)_{B-L}$ Model

TL;DR

This paper explores a $U(1)_{B-L}$ extended Standard Model with right-handed neutrinos and scalars, proposing a dark matter candidate that can explain the Galactic Centre gamma-ray excess and relic density simultaneously.

Contribution

It introduces a $U(1)_{B-L}$ model with a scalar dark matter candidate capable of addressing both gamma-ray excess and relic density constraints.

Findings

Dark matter mass range 40-55 GeV fits gamma-ray excess.

Model consistent with relic density, collider, and direct detection constraints.

Resonance region around the additional Higgs scalar enhances viability.

Abstract

In this work, we have considered a gauged $U(1)_{\rm B-L}$ extension of the Standard Model (SM) with three right handed neutrinos for anomaly cancellation and two additional SM singlet complex scalars with non-trivial B-L charges. One of these is used to spontaneously break the $U(1)_{\rm B-L}$ gauge symmetry, leading to Majorana masses for the neutrinos through the standard Type I seesaw mechanism, while the other becomes the dark matter (DM) candidate in the model. We test the viability of the model to simultaneously explain the DM relic density observed in the CMB data as well as the Galactic Centre (GC) $\gamma$-ray excess seen by Fermi-LAT. We show that for DM masses in the range 40-55 GeV and for a wide range of $U(1)_{\rm B-L}$ gauge boson masses, one can satisfy both these constraints if the additional neutral Higgs scalar has a mass around the resonance region. In studying the dark matter phenomenology and GC excess, we have taken into account theoretical as well as experimental constraints coming from vacuum stability condition, PLANCK bound on DM relic density, LHC and LUX and present allowed areas in the model parameter space consistent with all relevant data, calculate the predicted gamma ray flux from the GC and discuss the related phenomenology.