Antimatter Signatures of Gravitino Dark Matter Decay

TL;DR

This paper investigates how decaying gravitino dark matter could produce observable signals like positrons and gamma rays, potentially explaining existing astrophysical anomalies while highlighting challenges with antiproton flux predictions.

Contribution

It provides detailed calculations of positron and antiproton fluxes from gravitino decay, linking theoretical models with astrophysical observations and anomalies.

Findings

Gravitino with 150 GeV mass and 10^26 s lifetime can explain gamma ray and positron excesses.

Predicted antiproton flux may be too high but is uncertain and potentially compatible with data.

Results suggest indirect detection of gravitino dark matter is plausible but challenging due to flux uncertainties.

Abstract

The scenario of gravitino dark matter with broken R-parity naturally reconciles three paradigms that, albeit very well motivated separately, seem to be in mutual conflict: supersymmetric dark matter, thermal leptogenesis and standard Big Bang nucleosynthesis. Interestingly enough, the products of the gravitino decay could be observed, opening the possibility of indirect detection of gravitino dark matter. In this paper, we compute the positron and the antiproton fluxes from gravitino decay. We find that a gravitino with a mass of 150 GeV and a lifetime of 10^26 s could simultaneously explain the EGRET anomaly in the extragalactic diffuse gamma ray background and the HEAT excess in the positron fraction. However, the predicted antiproton flux tends to be too large, although the prediction suffers from large uncertainties and might be compatible with present observations for certain choices of propagation parameters.