Observation of the decay Λ b 0 → pK - μ + μ - and a search for CP violation

Abstract

A search for CP violation in the decay Λ b 0 → 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 Λ b 0 → pK - μ + μ - decay is observed for the first time, and two observables that are sensitive to different manifestations of CP violation are measured, Δ A_{CP}≡ A_{CP}({Λ}_b^0\to p{K}-{μ}+{μ}-)-{A}_{CP}({Λ}_b^0\to p{K}-J/ψ ) and a {a}_{CP}^{\widehat{T}- odd} , where the latter is based on asymmetries in the angle between the μ + μ - and pK - decay planes.