Observation of the Baryonic Flavor-Changing Neutral Current Decay Lambdab -> Lambda mu+ mu-
Abstract
We report the first observation of the baryonic flavor-changing neutral current decay Lambdab -> Lambda mu+ mu- with 24 signal events and a statistical significance of 5.8 Gaussian standard deviations. This measurement uses ppbar collisions data sample corresponding to 6.8fb-1 at sqrts=1.96TeV collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for Lambdab -> Lambda mu+ mu- are measured. We find B(Lambdab -> Lambda mu+ mu-) = [1.73+-0.42(stat)+-0.55(syst)] x 10-6. We also report the first measurement of the differential branching ratio of Bs -> phi mu+ mu- using 49 signal events. In addition, we report branching ratios for B+ -> K+ mu+ mu-, B0 -> K0 mu+ mu-, and B -> K*(892) mu+ mu- decays.