The Decay $b \to s \gamma$ In The Mssm Revisited

Abstract

We present a re-analysis of the decay $\bsgamma$ in the Minimal Supersymmetric Standard Model with radiatively induced breaking of $SU(2) \times U(1)$. We extend this analysis to regions of the supersymmetric parameter space wider than those previously studied. Results are explicitly presented for $m_t=150\GeV$. We emphasize the consequences for future searches of charged Higgs and charginos from a measurement of the branching ratio for this decay compatible with the Standard Model prediction. In spite of the strong sensitivity of this decay to the effects of supersymmetry, we find that, at the moment, no lower limit on the mass of these particles can be obtained. The large chargino contributions to the branching ratio for $\bsgamma$, for large values of $\tan \beta$, are effectively reduced by pushing the lightest eigenvalue of the up-squark mass matrix closer to the electroweak scale, i.e. by increasing the degree of degeneracy among the up-squarks.