Observation of electroweak production of W$\gamma$ with two jets in proton-proton collisions at $\sqrt{s} = $ 13 TeV

TL;DR

This paper reports the first observation of electroweak Wγ production with two jets in proton-proton collisions at 13 TeV, confirming theoretical predictions and setting constraints on anomalous gauge couplings.

Contribution

It provides the first observation of this process at 13 TeV and combines results with previous data, improving significance and measuring cross sections.

Findings

Significance of 4.9 sigma at 13 TeV

Combined significance of 5.3 sigma with previous data

Measured cross section of 20.4 fb for electroweak Wγjj production

Abstract

A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak W$\gamma$jj production in a restricted fiducial region is measured as 20.4 $\pm$ 4.5 fb and the total cross section for W$\gamma$ production in association with 2 jets in the same fiducial region is 108 $\pm$ 16 fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators.