MeV-GeV $\gamma$-ray telescopes probing axino LSP/gravitino NLSP as dark matter in the $\mu\nu$SSM

TL;DR

This paper explores how MeV-GeV gamma-ray telescopes can detect axino or gravitino dark matter in the $mbda$SSM, analyzing parameter space constraints and potential signals including a distinctive double-line signature.

Contribution

It provides a comprehensive analysis of axino and gravitino dark matter detection prospects within the $mbda$SSM, including novel predictions of double-line gamma-ray signals.

Findings

Axino or gravitino can produce detectable gamma-ray signals.

Parameter space constraints from neutrino and cosmological data are identified.

A unique double-line gamma-ray signature is predicted in certain scenarios.

Abstract

Axino and gravitino are promising candidates to solve the dark matter (DM) problem in the framework of supersymmetry. In this work, we assume that the axino is the lightest supersymmetric particle (LSP), and therefore contributes to DM. In the case of R-parity violating models, the axino can decay into a neutrino-photon pair with a lifetime much longer than the age of the Universe, yielding a potentially detectable signal. Interestingly, a gravitino next-to-LSP (NLSP) can live enough as to contribute to the relic density. We study both scenarios, only axino LSP as DM, and axino LSP with gravitino NLSP as DM. We carry out the analysis in the context of the $\mu\nu$SSM, which solves the $\mu$ problem and reproduces neutrino data, only adding couplings involving right-handed neutrinos. In particular, we perform a complete analysis of the relevant parameter space of the model considering constraints from neutrino physics, cosmological observations, and $\gamma$-ray detection. We find that the axino or the gravitino can produce a signal detectable by future MeV-GeV $\gamma$-ray telescopes. In addition, in a parameter region where we get a well-tempered mixture of both particles, a double-line signal arises as a smoking gun.