Dark matter allowed scenarios for Yukawa-unified SO(10) SUSY GUTs

TL;DR

This paper explores Yukawa-unified SO(10) SUSY GUT models, analyzing their parameter space with MCMC to find spectra consistent with dark matter relic density and predicts LHC signals such as gluino pair production with high b-jet multiplicity.

Contribution

It performs a comprehensive MCMC analysis of Yukawa-unified SO(10) SUSY models, identifying viable spectra and potential LHC signatures consistent with dark matter constraints.

Findings

Spectrum characterized by multi-TeV scalars and ~100 GeV gauginos.

Most solutions predict too high neutralino relic abundance.

Possible solutions include neutralino decay, non-universal gaugino masses, and Higgs resonance annihilation.

Abstract

Simple supersymmetric grand unified models based on the gauge group SO(10) require --in addition to gauge and matter unification-- the unification of t-b-\tau Yukawa couplings. Yukawa unification, however, only occurs for very special values of the soft SUSY breaking parameters. We perform a search using a Markov Chain Monte Carlo (MCMC) technique to investigate model parameters and sparticle mass spectra which occur in Yukawa-unified SUSY models, where we also require the relic density of neutralino dark matter to saturate the WMAP-measured abundance. We find the spectrum is characterizd by three mass scales: first/second generation scalars in the multi-TeV range, third generation scalars in the TeV range, and gauginos in the \sim 100 GeV range. Most solutions give far too high a relic abundance of neutralino dark matter. The dark matter discrepancy can be rectified by 1. allowing for neutralino decay to axino plus photon, 2. imposing gaugino mass non-universality or 3. imposing generational non-universality. In addition, the MCMC approach finds 4. a compromise solution where scalar masses are not too heavy, and where neutralino annihilation occurs via the light Higgs h resonance. By imposing weak scale Higgs soft term boundary conditions, we are also able to generate 5. low \mu, m_A solutions with neutralino annihilation via a light A resonance, though these solutions seem to be excluded by CDF/D0 measurements of the B_s\to \mu^+\mu^- branching fraction. Based on the dual requirements of Yukawa coupling unification and dark matter relic density, we predict new physics signals at the LHC from pair production of 350--450 GeV gluinos. The events are characterized by very high b-jet multiplicity and a dilepton mass edge around mz2-mz1 \sim 50-75 GeV.