Measurements of electroweak production of a photon in association with two jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports the first observation of electroweak production of a photon with two jets in proton-proton collisions at 13 TeV, measuring the cross section and setting limits on effective field theory operators.

Contribution

It provides the first measurement of this process at the LHC, confirming standard model predictions and constraining new physics via effective field theory.

Findings

Measured cross section: 202 +36/-32 fb

Significance exceeds five standard deviations

Set limits on Wilson coefficients c_W and c_HWB

Abstract

The first observation of electroweak production of a photon in association with two forward jets in proton-proton collisions is presented. The measurement uses data recorded by the CMS experiment at the LHC during 2016$-$2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis is performed in a region enriched in photon production via vector boson fusion, with a requirement on the transverse momentum of the photon to exceed 200 GeV. The cross section is measured to be 202 $^{+36}_{-32}$ fb, at a significance with respect to the null hypothesis that exceeds five standard deviations. This is in agreement with the standard model prediction of 177 $^{+13}_{-12}$ fb. Differential cross sections are measured as a function of various observables. Limits are set on dimension-6 effective field theory operators that contribute to the WW$\gamma$ interaction. The observed 95% confidence intervals for the corresponding Warsaw basis Wilson coefficients $c_\mathrm{W}$ and $c_\mathrm{HWB}$ are [$-$0.11, 0.16] and [$-$1.6, 1.5], respectively.