Possible new-physics signals in b → sγ and b → sl+l− Original Research Article

We consider possible new-physics contributions to b → sl+l− assuming that new-physics modifies (chromo) magnetic and electric form factors in b → sγy∗ and b → sγ with the same chirality structure as in the standard model. Parametrizing the new-physics effects on b → sψ∗ and b → sg in terms of four real parameters, one finds that there is a large enough region of parameter space in which the measured branching ratio for B → Xsγ can be accommodated, and the predicted CP violation effect could be as large as ∼ 30%. Moreover, the branching ratio and the forward-backward asymmetry of a lepton in B → Xsl+l− and the tau polarization asymmetry in B → Xsτ+τ− can deviate from the SM predictions by a factor of ∼- 2, which can be accessible at B-factories. We also discuss these observables in a specific class of supersymmetric models with gluino-mediated flavor changing neutral currents (FCNC).