Pure Gravity Mediation and Spontaneous B-L Breaking from Strong Dynamics

TL;DR

This paper explores how pure gravity mediation links supersymmetry breaking with B-L symmetry breaking through strong dynamics, predicting high-scale SUSY breaking and connecting neutrino masses to the gravitino mass.

Contribution

It proposes a model where B-L symmetry breaking is tied to SUSY breaking in pure gravity mediation, with implications for neutrino masses and the superparticle spectrum.

Findings

Heavy Majorana neutrino mass scale is proportional to gravitino mass.

High-scale SUSY breaking (around 1000 TeV) is favored for baryogenesis.

B-L gauge dynamics influence superparticle masses and model constraints.

Abstract

In pure gravity mediation (PGM), the most minimal scheme for the mediation of supersymmetry (SUSY) breaking to the visible sector, soft masses for the standard model gauginos are generated at one loop rather than via direct couplings to the SUSY-breaking field. In any concrete implementation of PGM, the SUSY-breaking field is therefore required to carry nonzero charge under some global or local symmetry. As we point out in this note, a prime candidate for such a symmetry might be B-L, the Abelian gauge symmetry associated with the difference between baryon number B and lepton number L. The F-term of the SUSY-breaking field then not only breaks SUSY, but also B-L, which relates the respective spontaneous breaking of SUSY and B-L at a fundamental level. As a particularly interesting consequence, we find that the heavy Majorana neutrino mass scale ends up being tied to the gravitino mass, Lambda_N ~ m_3/2. Assuming nonthermal leptogenesis to be responsible for the generation of the baryon asymmetry of the universe, this connection may then explain why SUSY necessarily needs to be broken at a rather high energy scale, so that m_3/2 >~ 1000 TeV in accord with the concept of PGM. We illustrate our idea by means of a minimal model of dynamical SUSY breaking, in which B-L is identified as a weakly gauged flavor symmetry. We also discuss the effect of the B-L gauge dynamics on the superparticle mass spectrum as well as the resulting constraints on the parameter space of our model. In particular, we comment on the role of the B-L D-term.