Neutralino dark matter,b−τYukawa unification, and nonuniversal sfermion masses

We study the implications of minimal nonuniversal boundary conditions in the sfermion soft supersymmetry breaking (SSB) masses of minimal supergravity. We impose asymptotic $b-\tau$ Yukawa coupling unification and we resort to a parametrization of the deviation from universality in the SSB motivated by the multiplet structure of the $\mathrm{SU}\left(5\right)\mathrm{}$ grand unified theory. A set of cosmophenomenological constraints, including the recent results from the Wilkinson Microwave Anisotropy Probe, determines the allowed parameter space of the models under consideration. We highlight a “new coannihilation corridor” where $\tilde{\chi }-b_1$ and $\tilde{\chi }-{\tilde{\tau }}_1-{\tilde{\nu }}_{\tau }$ coannihilations significantly contribute to the reduction of the neutralino relic density.