Observation of the Λ 0 b → J/ψ pπ − decay

Abstract

The first observation of the Cabibbo-suppressed decay Λ 0 b → J/ψpπ − is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. A prominent signal is observed and the branching fraction relative to the decay mode Λ 0 b → J/ψpK − is determined to be B(Λ0b→J/ψpπ−)B(Λ0b→J/ψpK−)=0.0824±0.0025 (stat)±0.0042 (syst).

A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be ACP(Λ0b→J/ψpπ−)−ACP(Λ0b→J/ψpK−)=(+5.7±2.4 (stat)±1.2 (syst))%,

which is compatible with CP symmetry at the 2.2σ level.