Gamma-Rays from Decaying Dark Matter
Gianfranco Bertone, Wilfried Buchmuller, Laura Covi, Alejandro Ibarra
TL;DR
The paper addresses the gamma-ray signatures of decaying dark matter, focusing on gravitino DM in R-parity breaking vacua. It develops the framework for indirect detection by deriving both extragalactic and Galactic-halo contributions to the gamma-ray flux, predicting monochromatic lines at $E_\gamma = m_{DM}/2$ and a redshifted extragalactic component, with fluxes proportional to $1/\tau_{DM}$. The authors provide explicit expressions for $dJ_{eg}/dE$ and $dJ_{halo}/dE$ and discuss how the halo-to-extragalactic flux ratio is of order unity for typical Milky Way halos, implying both components are important and yield distinct angular patterns. They also assess detection prospects with upcoming missions such as GLAST and AMS-02 and outline how decaying DM signatures can be distinguished from annihilating DM via energy spectral features and angular distributions, informing constraints on DM mass and lifetime.
Abstract
We study the prospects for detecting gamma-rays from decaying Dark Matter (DM), focusing in particular on gravitino DM in R-parity breaking vacua. Given the substantially different angular distribution of the predicted gamma-ray signal with respect to the case of annihilating DM, and the relatively poor (of order 0.1$^\circ$) angular resolution of gamma-ray detectors, the best strategy for detection is in this case to look for an exotic contribution to the gamma-ray flux at high galactic latitudes, where the decaying DM contribution would resemble an astrophysical extra-galactic component, similar to the one inferred by EGRET observations. Upcoming experiments such as GLAST and AMS-02 may identify this exotic contribution and discriminate it from astrophysical sources, or place significant constraints on the mass and lifetime of DM particles.