Observation of the Baryonic Flavor-Changing Neutral Current Decay Lambda(0)(b) -> Lambda mu(+)mu(-)

We report the first observation of the baryonic flavor-changing neutral current decay Lambda(0)(b) -> Lambda mu(+)mu(-) with 24 signal events and a statistical significance of 5.8 Gaussian standard deviations. This measurement uses a p (p) over bar collisions data sample corresponding to 6.8 fb(-1) at root s = 1.96 TeV collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for Lambda(0)(b) -> Lambda mu(+)mu(-) are measured. We find B(Lambda(0)(b) -> Lambda mu(+)mu(-)) = [1.73 +/- 0.42(stat) +/- (syst)] x 10(-6). We also report the first measurement of the differential branching ratio of B-s(0) -> phi mu(+)mu(-), using 49 signal events. In addition, we report branching ratios for B+ -> K+mu(+)mu(-), B-0 -> K-0 mu(+)mu(-), and B -> K*(892)mu(+)mu(-) decays.