Unstable gravitino dark matter and neutrino flux

Abstract

The gravitino is a promising supersymmetric dark matter candidatewhich does not require exact R-parity conservation.In fact, even with some small R-parity breaking, gravitinosare sufficiently long-lived to constitute the dark matter of the Universe,while yielding a cosmological scenario consistent with primordialnucleosynthesis and the high reheating temperature required for thermalleptogenesis. In this paper, we compute the neutrino flux from direct gravitinodecay and gauge boson fragmentation in a simple scenario withbilinear R-parity breaking. Our choice of parameters is motivated by a proposed interpretation of anomalies in the extragalactic gamma-ray spectrum and the positron fraction in terms of gravitino dark matter decay. We find that the generated neutrino flux is compatible with present measurements. We also discuss the possibility of detecting these neutrinos in present and future experiments and conclude that it is a challenging task. However, if detected, this distinctive signal might bring significant support to the scenario of gravitinos as decaying dark matter.