Gravitino Dark Matter in Gravity Mediation

TL;DR

This paper explores conditions under which the gravitino can be the lightest supersymmetric particle in gravity-mediated models, highlighting the roles of the Kaehler potential and gauge kinetic function, with implications for string theory.

Contribution

It derives general conditions for gravitino LSP in gravity mediation, linking model parameters to string-motivated setups.

Findings

Gravitino LSP occurs if gaugino mass > 2.5 times gravitino mass.

Condition ' < 0.2 derived for CMSSM models.

String-motivated models can satisfy these conditions.

Abstract

We study general conditions for the gravitino to be the lightest supersymmetric particle (LSP) in models with gravity mediated supersymmetry breaking. We find that the decisive quantities are the Kaehler potential K and the gauge kinetic function f. In constrained MSSM (CMSSM) type models, the gravitino LSP occurs if the gaugino mass at the GUT scale is greater than approximately 2.5 gravitino masses. This translates into \sqrt{K"}/f' < 0.2, where the derivatives are taken with respect to the dominant SUSY breaking field. This requirement can easily be satisfied in string-motivated setups.