SO(10) SUSY GUTs with mainly axion cold dark matter: implications for cosmology and colliders

Abstract

Supersymmetric grand unified theories based on the gauge group SO(10) are highly motivated. In the simplest models, one expects t—b—τ Yukawa coupling unification, in addition to gauge, matter and Higgs unification. Yukawa unification only occurs with very special GUT scale boundary conditions, leading to a spectra with ∼ 10 TeV first and second generation scalars, TeV‐scale third generation scalars, and light gauginos. The relic density of neutralino cold dark matter is calculated to be 102–104 times higher than observation. If we extend the theory with the PQ solution to the strong CP problem, then instead a mixture of axions and axinos comprises the dark matter, with the measured abundance. Such a solution solves several cosmological problems. We predict a rather light gluino with mg̃∼300–500 GeV that should be visible in either Tevatron or forthcoming LHC run 1 data. We would also expect ultimately a positive result from relic axion search experiments.