Gamma-ray signals from multicomponent scalar dark matter decays

TL;DR

This paper investigates gamma-ray signals from the decay of heavier scalar dark matter components into lighter ones, focusing on the decay channel producing two photons, and assesses observational constraints and detection prospects.

Contribution

It provides a detailed analysis of the $ ext{scalar dark matter} ightarrow ext{scalar} + 2 ext{ photons}$ decay channel, including width calculations and observational limits, within effective and UV complete models.

Findings

The $ ext{scalar} ightarrow ext{scalar} + 2 ext{ photons}$ decay can have a sizable branching ratio.

Current gamma-ray data constrain the decay width and parameter space.

Potential signals from sneutrino decay in the $ ilde{ u}$MSSM are briefly discussed.

Abstract

Within a multicomponent dark matter scenario, novel gamma-ray signals may arise from the decay of the heavier dark matter component into the lighter. For a scalar dark sector of this kind, the decay $\phi_2\rightarrow\phi_1 \gamma$ is forbidden by the conservation of angular momentum, but the decay $\phi_2 \rightarrow \phi_1 \gamma\gamma$ can have a sizable or even dominant branching ratio. In this paper we present a detailed study of this decay channel. We determine the width and photon energy spectrum generated in the decay, employing an effective theory approach, and in UV complete models where the scalar dark matter components interact with heavy or light fermions. We also calculate limits on the inverse width from current data of the isotropic diffuse photon flux, both for a hierarchical and a degenerate dark matter spectrum. Finally, we briefly comment on the prospects of observing the diphoton signal from sneutrino decay in the minimal supersymmetric standard model extended with right-handed neutrino superfields ($\tilde{\nu}$MSSM).