Measurement of CP asymmetries in Λ_b^0→ph^- decays

Abstract

A search for CP violation in Λ_b^0 -> pK^- and Λ_b^0 -> pπ^- decays is presented using the full Run 1 and Run 2 data samples of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 9 fb^-1 at center-of-mass energies of 7, 8, and 13 TeV. For the Run 2 data sample, the CP-violating asymmetries are measured to be: A_CP^(pK^-) = (-1.4 ± 0.7 ± 0.4)% and A_CP^(pπ^-) = (0.4 ± 0.9 ± 0.4)%, where the first uncertainty is statistical and the second is systematic. Following significant improvements in the evaluation of systematic uncertainties compared to the previous LHCb measurement, the Run 1 dataset is reanalyzed to update the corresponding results. When combining the Run 2 and updated Run 1 measurements, the final results are found to be: A_CP^(pK^-) = (-1.1 ± 0.7 ± 0.4)% and A_CP^(pπ^-) = (0.2 ± 0.8 ± 0.4)%,

constituting the most precise measurements of these asymmetries to date.