Precision luminosity measurement with proton-proton collisions at the CMS experiment in Run 2

TL;DR

This paper reports a highly precise measurement of the CMS detector's luminosity during LHC Run 2, using beam-separation scans and the Van der Meer method, with detailed systematic uncertainty analysis.

Contribution

It presents a comprehensive methodology for luminosity calibration at the LHC, including systematic uncertainty evaluation, achieving one of the most precise measurements at hadron colliders.

Findings

Achieved high-precision luminosity measurement for CMS during Run 2.

Identified key systematic uncertainties affecting luminosity calibration.

Demonstrated stability and linearity of the detector over the data-taking period.

Abstract

A precision luminosity measurement is essential for LHC cross-section measurements to determine fundamental parameters of the standard model and constrain or discover beyond-the-standard-model phenomena. The luminosity of the CMS detector has been measured at the LHC Interaction Point 5 using proton-proton collisions at $\sqrt{s}=13$ TeV during the Run 2 data-taking period (2015-2018). The absolute luminosity scale is obtained using beam-separation scans and the Van der Meer (VdM) method, and several systematic uncertainty sources are investigated, from the knowledge of the scale of beam separation provided by LHC magnets to the nonfactorizability of the spatial components of proton bunch density distributions in the transverse direction. When the VdM calibration is applied to the entire data-taking period, the detector linearity and stability measurements contribute significantly to the total uncertainty in the integrated luminosity. In 2016-2018, the reported integrated luminosity was among the most precise measurements at bunched-beam hadron colliders.