Probing new physics via precision CP violation measurements in charmless B-meson decays

ongoing

The amount of CP violation in the Standard Model (SM) of particle physics is not sufficient to explain the matter-antimatter asymmetry in the Universe, and thus searching for new CP-violating sources beyond the SM is of high priority in particle physics. The goal of this fellowship is to address this challenge by performing a novel measurement of CP violation simultaneously in the Bs -> KS K+ pi- and Bs -> KS K- pi+ decays. The two decays have dominant contributions from the b->s loop transition to which New Physics (NP) effects could have sizable contributions. The method will first be developed with a standalone study. This will investigate several factors that can affect the precision of the measurement of CP-violating observables in Bs -> KS K+- pi-+ decays, including the sample size and the amplitude model variations. This will provide crucial insight for the subsequent measurement using real data and future studies involving two final states. The LHCb experiment has collected a large sample of Bs -> KS K+- pi-+ decays to date, which is expected to increase significantly in the next two years. This data sample will be used to perform the first decay-time-dependent Dalitz-plot analysis to the KS K+ pi- and KS K- pi+ final states simultaneously, and to determine the associated CP-violating observables. The results of the analysis will provide a novel method to test the SM. The theoretical interpretation of in terms of potential NP sources of CP violation benefits from U-spin relations with the companion Bd -> KS K+- pi-+ decay, which can be used to control hadronic uncertainties. Analyses of the Bd modes will require larger data samples, which are not included in the baseline plan of this project. However, this project will set the stage for these measurements, developing all necessary methodology for a systematically improvable precise test of the SM.