Implications of $B \to \rho \gamma$ measurements in the standard model and supersymmetric theories

Abstract

We study the implications of the recently improved upper limits on the branching ratios for the decays B -> rho gamma, expressed as R(rho gamma/K^* gamma) = BR(B -> rho gamma)/BR(B -> K^* gamma) <0.047. We work out the constraints that the current bound on R(rho gamma/K^* gamma) implies on the parameters of the quark mixing matrix in the standard model (SM). Using the present profile of the unitarity triangle, we predict this ratio to be R(rho gamma/K^* gamma) = 0.023 +/- 0.012. We also work out the correlations involving R(rho gamma/K^* gamma), the isospin-violating ratio Delta (rho gamma), and the direct CP-violating asymmetry A_CP (rho gamma) in B -> rho gamma decays in the SM, in the minimal supersymmetric extension of the SM (MSSM), and in an extension of the MSSM involving an additional flavor-changing structure in b -> d transitions.