Light Stop and the $b\rightarrow sγ$ Process

Abstract

A constraint from $b\rightarrow sγ$ process to the minimal supersymmetric standard model is derived in the light stop region where the coupling between the lighter stop and the $Z^0$ boson vanishes due to the left-right mixing of the stop states. It is pointed out that although some region in the parameter space is excluded from this process there remains a large parameter space where the amplitude of the $b\rightarrow sγ$ is suppressed due to partial cancellation between different diagrams. Stop as light as 20 GeV is still viable from the $b\rightarrow sγ$ constraint.