Measurement of $CP$ asymmetries in $\Lambda_{b}^{0} \to pK^{-}$ and $\Lambda_{b}^{0} \to p\pi^-$ decays at LHCb

The LHCb experiment has been designed to perform precision measurements in the flavour physics sector at the Large Hadron Collider (LHC). The measurement of the CP-violating observable defined as ΔACP = ACP (Λ0b → pK − ) − ACP (Λ0b → pπ − ), where ACP (Λ0b → pK − ) and ACP (Λ0b → pπ − ) are the direct CP asymmetries in Λ0b → pK − and Λ0b → pπ − decays, is presented for the first time using LHCb data. Using the full 2011 and 2012 data sets of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of about 3 fb −1, the value ΔACP = (0.8 ± 2.1 ± 0.2)% is obtained. The first uncertainty is statistical and the second corresponds to one of the dominant systematic effects. As the result is compatible with zero, no evidence of CP violation is found. This is the most precise measurement of CP violation in the decays of baryons containing the b quark to date. Once the analysis will be completed with an exhaustive study of systematic uncertainties, the results will be published by the LHCb Collaboration.