b -> s gamma with large tan beta in a MSSM analysis constrained by a realistic SO(10) model - art. no. 095002

The study of the MSSM in the large tan beta regime has to include correlati ons between the constraints presented by the low energy values of the b qua rk mass and BR(b-->s gamma). Both quantities receive SUSY contributions enh anced by tan beta and have a major impact on the MSSM analysis. Here we sum marize the results of such a study constrained by a complete SO(10) model. The dominant effects to the analysis come from third generation Yukawa coup lings and a GUT threshold to alpha(s). We show that a small negative GUT co rrection to alpha(s) accommodates alpha(s)(M-Z) less than or equal to 0.118 and delta m(b)(SUSY) > 0. Since the latter quantity is positive this opens up two options to fit the measured rate for b-->s gamma. The two distinct fits differ by the overall sign of the amplitude for this process. They wor k equally well in complementary regions of the allowed SUSY parameter space . We show plots of the partial contributions to the coefficient C-7(M-Z) in the (m(0),M-1/2) plane in each of these best fits. We conclude that an att ractive SO(10)-derived regime of the MSSM remains a viable option. [S0556-2 821(99)01403-4].