Mixed Higgsino Dark Matter from a Large SU(2) Gaugino Mass

TL;DR

This paper investigates how non-universal gaugino masses at the GUT scale influence the Higgsino content of the lightest neutralino, leading to a viable dark matter candidate with distinctive collider signatures.

Contribution

It introduces a model with large SU(2) gaugino mass at the GUT scale, resulting in mixed Higgsino dark matter and unique phenomenological predictions.

Findings

Relic density of neutralino matches observed dark matter abundance.

Enhanced direct and indirect detection rates for neutralino dark matter.

LHC can discover SUSY with gluino masses up to 2350-2750 GeV.

Abstract

We observe that in SUSY models with non-universal GUT scale gaugino mass parameters, raising the GUT scale SU(2) gaugino mass |M_2| from its unified value results in a smaller value of -m_{H_u}^2 at the weak scale. By the electroweak symmetry breaking conditions, this implies a reduced value of \mu^2 {\it vis \`a vis} models with gaugino mass unification. The lightest neutralino can then be mixed Higgsino dark matter with a relic density in agreement with the measured abundance of cold dark matter (DM). We explore the phenomenology of this high |M_2| DM model. The spectrum is characterized by a very large wino mass and a concomitantly large splitting between left- and right- sfermion masses. In addition, the lighter chargino and three light neutralinos are relatively light with substantial higgsino components. The higgsino content of the LSP implies large rates for direct detection of neutralino dark matter, and enhanced rates for its indirect detection relative to mSUGRA. We find that experiments at the LHC should be able to discover SUSY over the portion of parameter space where m_{\tg} \alt 2350-2750 ~GeV, depending on the squark mass, while a 1 TeV electron-positron collider has a reach comparable to that of the LHC. The dilepton mass spectrum in multi-jet + \ell^+\ell^- + \eslt events at the LHC will likely show more than one mass edge, while its shape should provide indirect evidence for the large higgsino content of the decaying neutralinos.