Gravitino Dark Matter in R-Parity Breaking Vacua

TL;DR

This work shows that tiny R-parity and lepton-number breaking can reconcile a gravitino LSP with primordial nucleosynthesis and thermal leptogenesis when $m_{3/2}\gtrsim 5$ GeV. The authors present a concrete model in which R-parity violation is tied to B-L breaking, yielding naturally small couplings and a gravitino lifetime $\tau_{3/2}$ that allows DM while enabling observable decays to $\gamma\nu$ and distinctive NLSP signatures at colliders. Neutrino masses arise through an electroweak seesaw in the RPV framework, and cosmological and collider analyses predict gamma-ray signals and displaced NLSP decays that can be tested by GLAST and the LHC. Moreover, the framework offers a path to a microscopic determination of the Planck mass from gravitino observables, linking collider physics to Planck-scale physics.

Abstract

We show that in the case of small R-parity and lepton number breaking couplings, primordial nucleosynthesis, thermal leptogenesis and gravitino dark matter are naturally consistent for gravitino masses m_{3/2} \gsim 5 GeV. We present a model where R-parity breaking is tied to B-L breaking, which predicts the needed small couplings. The metastable next-to-lightest superparticle has a decay length that is typically larger than a few centimeters, with characteristic signatures at the LHC. The photon flux produced by relic gravitino decays may be part of the apparent excess in the extragalactic diffuse gamma-ray flux obtained from the EGRET data for a gravitino mass m_{3/2} \sim 10 GeV. In this case, a clear signal can be expected from GLAST in the near future.