Gravitino Dark Matter in Tree Level Gauge Mediation with and without R-parity

Preprint number: CP3-Origins-2011-34 and DIAS-2011-26
Authors: Giorgio Arcadi (SISSA and INFN), Luca Di Luzio (SISSA and INFN), and Marco Nardecchia (CP3-Origins and DIAS)
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We investigate the cosmological aspects of Tree level Gauge Mediation, a recently proposed mechanism in which the breaking of supersymmetry is communicated to the soft scalar masses by extra gauge interactions at the tree level. Embedding the mechanism in a Grand Unified Theory and requiring the observability of sfermion masses at the Large Hadron Collider, it follows that the Lightest Supersymmetric Particle is a gravitino with a mass of the order of 10 GeV. The analysis in the presence of R-parity shows that a typical Tree level Gauge Mediation spectrum leads to an overabundance of the Dark Matter relic density and a tension with the constraints from Big Bang Nucle- osynthesis. This suggests to relax the exact conservation of the R-parity. The underlying SO(10) Grand Unified Theory together with the bounds from proton decay provide a ra- tionale for considering only bilinear R-parity violating operators. We finally analyze the cosmological implications of this setup by identifying the phenomenologically viable regions of the parameter space.