Rare Decays in LHCb

Abstract

The rare B decays Bs(d)-->\mu\mu, B-->K*\mu\mu and Bs-->\phi\gamma are studied using up to \sim 0.41 fb^{-1} of pp collisions at \sqrt{s} = 7 TeV collected by the \lhcb experiment in 2010 and 2011. A search for the decays Bs(d)-->\mu\mu, is performed with 0.41 fb^{-1} . The absence of significant signal leads to BR(Bs-->\mu\mu<1.4 x 10^{-8} and BR(Bd-->\mu\mu<3.2 x 10^{-9} at 95% confidence level. The forward-backward asymmetry, fraction of longitudinal polarization and differential branching fraction of B-->K*\mu\mu, as a function of dimuon invariant mass, are measured in 0.31 fb^{-1}. The ratio of branching ratios of the radiative B decays B--> K*\gamma and Bs-->\phi\gamma h as been measured using 0.34fb^{-1}. The obtained value for the ratio is 1.52 \pm 0.14 (stat) \pm 0.10 (syst) \pm 0.12 (f_s/f_d). Using the HFAG value for BR(Bd --> K^*\gamma), BR(Bs-->\phi\gamma) has been found to be (2.8 \pm 0.5)\times 10^{-5}.