Study of charm mixing and CP violation with D0 → K±π∓π±π∓ decays

Abstract

A study of charm mixing and CP violation in D0 → K±π∓π±π∓ decays is performed using data collected by the LHCb experiment in proton-proton collisions from 2015 to 2018, corresponding to an integrated luminosity of 6 fb−1. The ratio of promptly produced D0 → K+π−π+π− to D0 → K−π+π−π+ decay rates is measured as a function of D0 decay time, both inclusive over phase space and in bins of phase space. Taking external inputs for the D 0 − D ¯ 0 mixing parameters x and y allows constraints to be obtained on the hadronic parameters of the charm decay. When combined with previous measurements from charm-threshold experiments and at LHCb, improved knowledge is obtained for these parameters, which is valuable for studies of the angle γ of the Unitarity Triangle. An alternative analysis is also performed, in which external inputs are taken for the hadronic parameters, and the mixing parameters are determined, including ∆x and ∆y, which are nonzero in the presence of CP violation. It is found that x = 0 . 85 − 0.24 + 0.15 % , y = 0 . 21 − 0.27 + 0.29 % , ∆x = (−0.02 ± 0.04) % and Δ y = 0.0 2 − 0.03 + 0.04 % . These results are consistent with previous measurements and the hypothesis of CP conservation.