3.5 keV x-ray line from decaying gravitino dark matter

Understand

Extremely weakly interacting particles like the gravitino may be stable enough on cosmological time scales to constitute a good dark matter candidate even in the presence of R-parity violation.

• We consider the possibility that the recently identified 3.5 keV x-ray line can be generated in light gravitino decays to neutrinos and photons.
• We find that this is indeed possible in loop processes induced by trilinear lepton-number-violating couplings.
• We show that in order to avoid overproduction of gravitinos, the reheating temperature has to be at most around 100 GeV to 1 TeV.