Any Questions?

Magic 12/13/2014, 7:38 pm

Monochromatic photons could be produced in the annihilation or decay of dark matter particles.

At high energies, the search for such line features in the cosmic gamma-ray spectrum is essentially background free because plausible astrophysical processes are not expected to produce such a signal.

The observation of a gamma-ray line would hence be a `smoking-gun' signature for dark matter, making the search for such signals particularly attractive.

Among the different dark matter models predicting gamma-ray lines, the local supersymmetric extension of the standard model with small R-parity violation and gravitino LSP is of particular interest because it provides a framework where primordial nucleosynthesis, gravitino dark matter and thermal leptogenesis are naturally consistent.

Using the two-years Fermi LAT data, we present a dedicated search for gamma-ray lines coming from dark matter annihilation or decay in the Galactic halo.

Taking into account the full detector response, and using a binned profile likelihood method, we search for significant line features in the energy spectrum of the diffuse flux observed in different regions of the sky.

No evidence for a line signal at the 5-sigma level is found for photon energies between 1 and 300 GeV, and conservative bounds on dark matter decay rates and annihilation cross sections are presented. Implications for gravitino dark matter in presence of small R-parity violation are discussed, as well as the impact of our results on the prospect for seeing long-lived neutralinos or staus (stau is a slepton) at the LHC.