Study of charge asymmetries in pion and kaon identification with the Belle II detector

In this work, we study the performance of the charged kaon and pion identification at the Belle II experiment. The analysed data set corresponds to an integrated luminosity of 404 fb^-1, the data were collected from 2019 to 2022 and are compared with Monte Carlo simulation. Efficiencies and mis-identification rates of kaons and pions are measured using a sample of Ds+ to phi(K+K-) pi+, they are defined as the ratio of signal yields after and before applying the identification selection to particle tracks. The signal yields are determined from fits to the invariant mass distributions of the resonances involved. Several preselection criteria are applied to reduce the background. The identification observables are studied as a function of the main kinematic variables: momentum p and cos(theta). Furthermore, we measure the corresponding charge asymmetries and make a comparison of the results obtained from both real data and simulation. The goal is to determine whether the experimental data show significant charge asymmetries compared to those observed with the simulation. This study describes the performance of global particle identification at Belle II. In addition, we discuss the inclusion of calibration weights and evaluate the performance of individual sub-detectors.