Yukawa unification and neutralino dark matter inSU(4)c×SU(2)L×SU(2)R

We consider a left-right symmetric $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$ (4-2-2) model with gravity mediated supersymmetry breaking. We find that with 4-2-2 compatible nonuniversal gaugino masses, $t-b-\tau$ Yukawa coupling unification is consistent with neutralino dark matter abundance and with constraints from collider experiments (except $(g-2{)}_{\mu }$). The gluino mass lies close to that of the lightest neutralino, so that the gluino coannihilation channel plays an important role in determining the neutralino relic abundance. By relaxing the Yukawa unification constraint we find stau and stop masses as low as 200–220 GeV. We highlight some benchmark points for these cases with $40\le \tan \beta \le 58$.