A light neutralino in hybrid models of supersymmetry breaking

TL;DR

The work shows that gauge mediation models with messenger masses set by the SU(5) adjoint can produce a generalized GMSB spectrum featuring a light bino-like neutralino LSP, while gravity mediation supplies the correct $μ$ and $Bμ$ for electroweak breaking. By embedding an ISS-based SUSY-breaking sector and coupling it to a messenger sector with SU(5)–split masses, the authors derive a metastable vacuum and Planck-suppressed operators that generate $μ$ and $Bμ$ in the required range. A key result is that $M_1^{GMSB}=0$ at leading order due to the hypercharge embedding, forcing the bino to be light and the LSP, with $M_2$ and $M_3$ tied to the gauge mediation scale and dependent on the messenger representation. The framework yields distinctive low-energy phenomenology including non–universal gaugino masses, a light neutralino dark matter candidate, and cosmological constraints that can be satisfied in viable regions, offering clear experimental tests at colliders and in dark matter experiments.

Abstract

We show that in gauge mediation models where heavy messenger masses are provided by the adjoint Higgs field of an underlying SU(5) theory, a generalized gauge mediation spectrum arises with the characteristic feature of having a neutralino LSP much lighter than in the standard gauge or gravity mediation schemes. This naturally fits in a hybrid scenario where gravity mediation, while subdominant with respect to gauge mediation, provides mu and Bmu parameters of the appropriate size for electroweak symmetry breaking.