Constraints on supersymmetric grand unification fromb→sγ decay

Abstract

The top-quark Yukawa infrared fixed-point solution of the renormalization group equations, with minimal supersymmetry and grand unification, defines a low-energy spectrum of supersymmetric particle masses in terms of a few GUT-scale parameters assuming universal boundary conditions. We give predictions in this model for the inclusive b→sγ branching fraction and investigate the impact of nonuniversal scalar mass boundary conditions. We find our results do not depend significantly on the value of the GUT-scale trilinear coupling ${\mathit{A}}^{\mathit{G}}$. The small tanβ region favors predictions for the inclusive b→sγ branching fraction close to that of the standard model value. Nevertheless, forthcoming experimental results can eliminate some regions of the GUT parameter space.