Modulino as natural candidate for a sterile neutrino

Abstract

We discuss the possible generation of R-parity violating bilinear terms $ \mu_i\bar L_i H_2$ in both cases of gravity and gauge mediated supersymmetry breaking. Some phenomenological aspects are reviewed. In particular for scenario where $ \mu_i$ depend on the vacuum expectation values of some fields $S$, its fermionic partner $\tilde S$ plays the role of a sterile neutrino. This situation is quiet generic in the case of models arising from M-theory where $S$ is a modulus field. Observable effects are expected to be seen if the mass and mixing of $\tilde S$ with active neutrinos lie in an interesting region of parameters. This is naturally the case in gauge mediated supersymmetry breaking and some class of no-scale supergravity models where the gravitino mass is very small. For models with gravitino mass $m_{3/2}\sim$ TeV, we discuss the possibility that the modulino mass is of the order of $m^2_{3/2}/M_{Pl}$.