Development of a data-driven method to determine reconstruction efficiencies in the LHCb tracking detectors and study of the detector performance in Run 3

The LHCb experiment is a highly complex apparatus dedicated to measuring the decays of particles containing b- and c-quarks. During Run 3 of the Large Hadron Collider (LHC), protons collide at the interaction point of LHCb with an instantaneous luminosity of up to 2x10^33 cm^(-2)s^(-1) at a centre-of-mass energy of sqrt(s)=13.6 TeV. A full understanding of the detector and reconstruction efficiencies involved in the data acquisition is essential for many high precision measurements. A tag-and-probe method is developed to estimate the track reconstruction efficiency of the LHCb tracking subdetectors exploiting the decay of J/psi->mu mu. Discrepancies of the measured track reconstruction efficiencies between simulated and recorded data are studied and used to derive correction factors. An agreement between recorded and simulated data at the sub-percent level is achieved over almost the entire phase space and for all tracking subdetectors, illustrating an excellent understanding of the upgraded LHCb detector and its reconstruction sequences. A novel approach to derive the effect of interactions in the detector material is developed and used to provide first estimates, which contribute a systematic uncertainty on the order of a few percent to the track reconstruction efficiency. Further corrections are expected to reduce this systematic uncertainty to the order of one percent or less.