Light Higgsinos as Heralds of Higher-Dimensional Unification

TL;DR

This paper explores how higher-dimensional grand-unified models can produce a hybrid supersymmetry breaking pattern, resulting in light higgsinos and heavy superpartners, with implications for dark matter.

Contribution

It demonstrates a novel hybrid gauge and gravity mediation mechanism in higher-dimensional GUT models leading to distinctive superpartner spectra.

Findings

Light, near-degenerate higgsinos below 200 GeV

Other superpartners are significantly heavier, from 500 GeV to several TeV

Gravitino as the potential dark matter candidate

Abstract

Grand-unified models with extra dimensions at the GUT scale will typically contain exotic states with Standard Model charges and GUT-scale masses. They can act as messengers for gauge-mediated supersymmetry breaking. If the number of messengers is sizeable, soft terms for the visible sector fields will be predominantly generated by gauge mediation, while gravity mediation can induce a small mu parameter. We illustrate this hybrid mediation pattern with two examples, in which the superpartner spectrum contains light and near-degenerate higgsinos with masses below 200 GeV. The typical masses of all other superpartners are much larger, from at least 500 GeV up to several TeV. The lightest superparticle is the gravitino, which may be the dominant component of dark matter.