Improved model-independent analysis of semileptonic and radiative rareBdecays

Abstract

We update the branching ratios for the inclusive decays $B\to X_s \ell^+ \ell^-$ and the exclusive decays $B\to (K,K^*) \ell^+ \ell^-$, with $\ell=e, \m$, in the standard model by including the explicit $O(\a_s)$ and $\Lambda_{\hbox{\tiny QCD}} / m_b$ corrections. This framework is used in conjunction with the current measurements of the branching ratios for $B\to X_s \g$ and $B\to K \ell^+ \ell^-$ decays and upper limits on the branching ratios for the decays $B\to (K^*,X_s) \ell^+ \ell^-$ to work out bounds on the Wilson coefficients $C_7$, $C_8$, $C_9$ and $C_{10}$ appearing in the effective Hamiltonian formalism. The resulting bounds are found to be consistent with the predictions of the standard model and some variants of supersymmetric theories. We illustrate the constraints on supersymmetric parameters that the current data on rare B decays implies in the context of minimal flavor violating model and in more general scenarios admitting additional flavor changing mechanisms. Precise measurements of the dilepton invariant mass distributions in the decays $B \to (X_s,K^*,K) \ell^+ \ell^-$, in particular in the lower dilepton mass region, and the forward-backward asymmetry in the decays $B \to (X_s,K^*) \ell^+ \ell^-$, will greatly help in discriminating among the SM and various supersymmetric theories.