Observation of the Baryonic Flavor-Changing Neutral Current Decay Lambda_b -> Lambda mu+ mu-

TL;DR

This paper reports the first observation of the baryonic decay Lambda_b -> Lambda mu+ mu-, measuring its branching ratio and differential distribution, providing new insights into flavor-changing neutral currents in baryons.

Contribution

It presents the first observation and measurement of the Lambda_b -> Lambda mu+ mu- decay, including total and differential branching ratios, using data from the Tevatron collider.

Findings

First observation of Lambda_b -> Lambda mu+ mu- decay

Measured branching ratio B(Lambda_b -> Lambda mu+ mu-) = (1.73+-0.42(stat)+-0.55(syst)) x 10^{-6}

Reported differential branching ratio and other related decay modes.

Abstract

We report the first observation of the baryonic flavor-changing neutral current decay Lambda_b -> 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 sqrt{s}=1.96TeV collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for Lambda_b -> Lambda mu+ mu- are measured. We find B(Lambda_b -> 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 B_s -> 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.