Luminosity Determination by ALICE during LHC Run 3

Luminosity is a crucial component for measuring the cross-section of physical processes. The ALICE collaboration uses dedicated calibration data, the van der Meer (vdM) scans, to normalize luminosity detectors’s count rate to well-known (visible) cross sections. The needed information comes from LHC instrumentation and ALICE detectors. In the LHC Run 2, three trigger detectors (T0—Cherenkov detector, V0—scintillator, and ZDC—zero degree calirimeter) participated in the luminosity analysis of different colliding systems: pp, p–Pb, and Pb–Pb. During the LHC Long Shutdown 2, a new fast interacting trigger (FIT) detector was integrated with the ALICE setup. This paper gives a preliminary overview of FIT’s performance as the new ALICE luminometer and trigger detector. In addition to the latest data collected during the first pp collisions of Run 3, LHC Run 2 luminosity results are shown and discussed.