CERN Accelerating science

In this work, the performance of the identification of electrons and misidentification of pions as electrons are measured for 2024 LHCb data. The detector and the reconstruction have changed significantly for Run 3, so it is important to validate the electron identification performance with the early data. High-statistics and high-purity calibration samples collected in the calibration stream of the high-level trigger are used to evaluate the electron identification performance using the tag-and-probe method. The decay channel chosen for the evaluation of the identification efficiencies is $B \to J/\psi (\to ee) K$, whereas for the misidentification, the $D^* \to D^0 (\to K \pi) \pi$ is used. The method to obtain the efficiencies involves a BDT that is trained to efficiently discriminate signal from combinatorial background. Then, simultaneous fits to the "all" and "pass" samples were performed to obtain electron identification and pion misidentification efficiencies.