Gamma Ray Spectrum from Gravitino Dark Matter Decay

TL;DR

The energy spectrum of photons from gravitino decay is computed and its main qualitative features are discussed, revealing a diffuse gamma-ray flux with characteristic spectrum that could be measured in future experiments, such as GLAST or AMS-02.

Abstract

Gravitinos are very promising candidates for the cold dark matter of the Universe. Interestingly, to achieve a sufficiently long gravitino lifetime, R-parity conservation is not required, thus preventing any dangerous cosmological influence of the next-to-lightest supersymmetric particle. When R-parity is violated, gravitinos decay into photons and other particles with a lifetime much longer than the age of the Universe, producing a diffuse gamma ray flux with a characteristic spectrum that could be measured in future experiments, like GLAST or AMS-02. In this letter we compute the energy spectrum of photons from gravitino decay and discuss its main qualitative features.

Figures (1)

• Figure 1: Contributions to the total gamma ray flux for $m_{3/2}=150\,\text{GeV}$ and $\tau_{3/2}\simeq 2\times 10^{26}\text{s}$ compared to the EGRET data. In dotted lines we show the photon flux from the fragmentation of the $Z$ boson, in dashed lines from the fragmentation of the $W$ boson, and in dot-dashed lines from the two body decay $\psi_{3/2}\rightarrow \gamma \nu$. The background is shown as a long dashed line, while the total flux received is shown as a thick solid line.