Measurement of the production cross section for a W boson in association with a charm quark in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper measures the production cross section of W bosons with charm quarks in proton-proton collisions at 13 TeV, providing precise data to probe the proton's strange quark content and compare with advanced QCD predictions.

Contribution

It presents the most precise measurements to date of W+c production cross sections and their ratios at 13 TeV, improving understanding of proton structure and testing QCD calculations.

Findings

W+c cross section measured with high precision

Cross section ratio $R^ extpm_c$ determined to 1% accuracy

Results agree with next-to-next-to-leading order QCD predictions

Abstract

The strange quark content of the proton is probed through the measurement of the production cross section for a W boson and a charm (c) quark in proton-proton collisions at a center-of-mass energy of 13 TeV. The analysis uses a data sample corresponding to a total integrated luminosity of 138 fb$^{-1}$ collected with the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged using the presence of a muon or a secondary vertex inside the jet. The W+c production cross section and the cross section ratio $R^\pm_\text{c}$ = $\sigma$(W$^+$+$\bar{\text{c}}$) / $\sigma$(W$^-$+$\text{c}$) are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton originating from the W boson decay. The precision of the measurements is improved with respect to previous studies, reaching 1% in $R^\pm_\text{c}$. The precision of the measurements is improved with respect to previous studies, reaching 1% in $R^\pm_\text{c}$ = 0.950 $\pm$ 0.005 (stat) $\pm$ 0.010 (syst). The measurements are compared with theoretical predictions up to next-to-next-to-leading order in perturbative quantum chromodynamics.