Probing Gravitino Dark Matter with PAMELA and Fermi

TL;DR

This paper investigates the potential of decaying gravitino dark matter to explain cosmic-ray observations, finding that astrophysical sources are needed and that gamma-ray measurements can constrain such models.

Contribution

It provides a model-independent analysis of gravitino decay signatures and links cosmic-ray data with gamma-ray constraints and collider prospects.

Findings

Gravitino mass is constrained below 600 GeV by cosmological considerations.

Decaying gravitino dark matter cannot fully explain PAMELA and Fermi LAT data alone.

Gamma-ray lines below 300 GeV could indicate gravitino decay signatures.

Abstract

We analyze the cosmic-ray signatures of decaying gravitino dark matter in a model independent way based on an operator analysis. Thermal leptogenesis and universal boundary conditions at the GUT scale restrict the gravitino mass to be below 600 GeV. Electron and positron fluxes from gravitino decays, together with the standard GALPROP background, cannot explain both, the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. For gravitino dark matter, the observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribution of decaying gravitinos to the gamma-ray spectrum, in particular a line at an energy below 300 GeV. Future measurements of the gamma-ray flux will provide important constraints on possible signatures of decaying gravitino dark matter at the LHC.