CERN Accelerating science

Article
Title	Beam-beam interaction-induced bias to precision luminosity measurement
Author(s)	Wanczyk, Joanna (CERN ; Ecole Polytechnique, Lausanne) ; Buffat, Xavier (CERN) ; Dabrowski, Anne (CERN) ; Kozanecki, Witold (IRFU, Saclay) ; Pieloni, Tatiana (Ecole Polytechnique, Lausanne) ; Stickland, David (Princeton U.) ; Tomas Garcia, Rogelio (CERN) ; Wu, Yi (Ecole Polytechnique, Lausanne)
Publication	2024
Number of pages	8
In:	PoS EPS-HEP2023 (2024) 624
In:	2023 European Physical Society Conference on High Energy Physics (EPS-HEP2023), Hamburg, Germany, 20 - 25 Aug 2023, pp.624
DOI	10.22323/1.449.0624
Subject category	Accelerators and Storage Rings
Abstract	The mutual electromagnetic interaction between counter-rotating bunches crossing at the interaction points (IPs) of a particle collider has been studied since the dawn of the storage-ring era. It can result in a significant bias to absolute-luminosity calibrations determined by the van der Meer (vdM) method. Numerical models developed to study such beam—beam-induced biases at a single IP of the Large Hadron Collider (LHC) have been recently extended to better account for actual operating conditions, such as head-on collisions at non-scanning IPs during vdM scans, or scans performed during physics data-taking using higher-brightness beams than used during vdM-calibration sessions.As part of a long-term effort aimed at quantifying the beam-beam bias to luminosity-related observables in hadron colliders, in this paper we compare results from a dedicated beam-beam experiment performed at the LHC in 2022 to the predictions of the numerical model. We also report some preliminary observations about the impact of the beam-beam interaction on the instantaneous luminosity during physics operation, and investigate beam-beam contributions to the apparent non-linearity and overall stability of experimental luminometers during physics data taking.
Copyright/License	CC-BY-NC-ND-4.0

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