Measurement of W ± γ differential cross sections in proton-proton collisions at √ s = 13 TeV and effective field theory constraints

Abstract

Differential cross section measurements of W ± γ production in proton-proton collisions at √ 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 W W γ vertex are determined within an effective field theory framework, focusing on the O 3 W 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 O 3 W contribution than using the transverse momentum alone.