Measurement of W$^\pm\gamma$ differential cross sections in proton-proton collisions at $\sqrt{s}$ = 13 TeV and effective field theory constraints

TL;DR

This paper reports precise measurements of W±γ production cross sections at 13 TeV, compares them with advanced theoretical predictions, and sets constraints on new physics affecting the WWγ vertex using an innovative two-dimensional analysis approach.

Contribution

It provides the first detailed differential cross section measurements of W±γ production at 13 TeV and introduces a novel two-dimensional analysis to enhance sensitivity to new physics effects.

Findings

Measured differential cross sections agree with standard model predictions.

The two-dimensional analysis improves sensitivity to effective field theory operators.

Constraints on the $ ext{O}_ ext{3W}$ operator are established.

Abstract

Differential cross section measurements of W$^\pm\gamma$ production in proton-proton collisions at $\sqrt{s}$ = 13 TeV are presented. The data set used in this study was collected with the CMS detector at the CERN LHC in 2016-2018 with an integrated luminosity of 138 fb$^{-1}$. Candidate events containing an electron or muon, a photon, and missing transverse momentum are selected. The measurements are compared with standard model predictions computed at next-to-leading and next-to-next-to-leading orders in perturbative quantum chromodynamics. Constraints on the presence of TeV-scale new physics affecting the WW$\gamma$ vertex are determined within an effective field theory framework, focusing on the $\mathcal{O}_\mathrm{3W}$ operator. A simultaneous measurement of the photon transverse momentum and the azimuthal angle of the charged lepton in a special reference frame is performed. This two-dimensional approach provides up to a factor of ten more sensitivity to the interference between the standard model and the $\mathcal{O}_\mathrm{3W}$ contribution than using the transverse momentum alone.