A decaying neutralino as dark matter and its gamma ray spectrum

TL;DR

This paper proposes a model where a decaying neutralino in a supergravity framework acts as dark matter, producing gamma rays detectable by current and future telescopes, with a focus on its decay into a hidden sector neutralino.

Contribution

It introduces a concrete supergravity model with a hidden sector that allows the neutralino to decay with a lifetime exceeding the universe's age, providing a new dark matter candidate.

Findings

Neutralino decay can produce observable gamma rays.

Model predicts gamma ray signatures detectable by Fermi-LAT, SKA, and CTA.

Consistent with antiproton background measurements.

Abstract

It is shown that a decaying neutralino in a supergravity unified framework is a viable candidate for dark matter. Such a situation arises in the presence of a hidden sector with ultraweak couplings to the visible sector where the neutralino can decay into the hidden sector's lightest supersymmetric particle (LSP) with a lifetime larger than the lifetime of the universe. We present a concrete model where the MSSM/SUGRA is extended to include a hidden sector comprised of $U(1)_{X_1} \times U(1)_{X_2}$ gauge sector and the LSP of the hidden sector is a neutralino which is lighter than the LSP neutralino of the visible sector. We compute the loop suppressed radiative decay of the visible sector neutralino into the neutralino of the hidden sector and show that the decay can occur with a lifetime larger than the age of the universe. The decaying neutralino can be probed by indirect detection experiments, specifically by its signature decay into the hidden sector neutralino and an energetic gamma ray photon. Such a gamma ray can be searched for with improved sensitivity at Fermi-LAT and by future experiments such as the Square Kilometer Array (SKA) and the Cherenkov Telescope Array (CTA). We present several benchmarks which have a natural suppression of the hadronic channels from dark matter annihilation and decays and consistent with measurements of the antiproton background.