Observation of the decay Λb0 → pK−μ+μ− and a search for CP violation

Abstract

A search for CP violation in the decay Λb0 → pK−μ+μ− is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of CP violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of 3 fb−1. The Λb0 → pK−μ+μ− decay is observed for the first time, and two observables that are sensitive to different manifestations of CP violation are measured, ΔACP≡ACPΛb0→pK−μ+μ−−ACPΛb0→pK−J/ψ and aaCPT^‐odd, where the latter is based on asymmetries in the angle between the μ+μ− and pK− decay planes.These are measured to be ΔACP=−3.5±5.0stat±0.2syst×10−2,aCPT^‐odd=1.2±5.0stat±0.7syst×10−2,and no evidence for CP violation is found