Luminosity at LHCb in Run 3

TL;DR

This paper discusses the upgraded LHCb detector's new luminosity measurement methods during Run 3, highlighting improved stability, calibration, and early data-taking results at increased luminosity levels.

Contribution

Introduction of new luminosity measurement techniques and detectors for Run 3, enabling stable operation at higher luminosity with improved calibration procedures.

Findings

Successful implementation of new luminosity counters

Stable luminosity measurements during early Run 3 data

Enhanced calibration methods verified linearity

Abstract

The LHCb detector optimised its performance in Runs~1 and~2 by stabilising the instantaneous luminosity during a fill. This was achieved by tuning the distance between the two colliding beams according to the measurement of instantaneous luminosity from hardware-based trigger counters. The upgraded LHCb detector operates at fivefold instantaneous luminosity compared to the previous runs, and it has a fully software-based trigger. Consequently, a new approach to the luminosity measurement is adopted. New counters, with particular attention to maximum stability in time, and a new dedicated detector have been introduced for Run~3. Additionally, in order to verify linearity from calibration to data taking conditions, per-fill emittance scans are performed. We present an overview of the newly implemented methods for luminosity measurement, as well as early achievements obtained during the first few weeks of data taking.