Scenarios for Gluino Coannihilation

TL;DR

This paper explores supersymmetric models with gluino coannihilation, identifying parameter regions where gluino and LSP masses are nearly degenerate, affecting dark matter relic density and constrained by collider and cosmological data.

Contribution

It introduces and analyzes two supersymmetric scenarios with gluino coannihilation, including non-universal gaugino masses and vector-like supermultiplets, detailing their parameter spaces and phenomenological constraints.

Findings

LSP masses up to ~8 TeV can achieve correct dark matter density.

Gluino nearly degenerate with LSP in models with vector-like supermultiplets.

Parameter space constrained by electroweak symmetry breaking and Higgs mass.

Abstract

We study supersymmetric scenarios in which the gluino is the next-to-lightest supersymmetric particle (NLSP), with a mass sufficiently close to that of the lightest supersymmetric particle (LSP) that gluino coannihilation becomes important. One of these scenarios is the MSSM with soft supersymmetry-breaking squark and slepton masses that are universal at an input GUT renormalization scale, but with non-universal gaugino masses. The other scenario is an extension of the MSSM to include vector-like supermultiplets. In both scenarios, we identify the regions of parameter space where gluino coannihilation is important, and discuss their relations to other regions of parameter space where other mechanisms bring the dark matter density into the range allowed by cosmology. In the case of the non-universal MSSM scenario, we find that the allowed range of parameter space is constrained by the requirement of electroweak symmetry breaking, the avoidance of a charged LSP and the measured mass of the Higgs boson, in particular, as well as the appearance of other dark matter (co)annihilation processes. Nevertheless, LSP masses $m_\chi \lesssim 8$~TeV with the correct dark matter density are quite possible. In the case of pure gravity mediation with additional vector-like supermultiplets, changes to the anomaly-mediated gluino mass and the threshold effects associated with these states can make the gluino almost degenerate with the LSP, and we find a similar upper bound.