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.
Highlights
The measurement of the properties of vector boson pair production is an important test of the electroweak sector of the standard model (SM)
Interference between the leading order (LO) WÆγ production diagrams results in a cross section that vanishes in specific phase space regions. This effect is known as a radiation amplitude zero (RAZ) [7–11]
An effective field theory (EFT) approach can be used to study how new physics entering at an energy scale Λ, assumed to be much larger than the electroweak scale, leads to deviations from the SM at an energy regime accessible at the LHC
Summary
The measurement of the properties of vector boson pair production is an important test of the electroweak sector of the standard model (SM). The CMS Collapboffiffiration has performed the first WÆγ measurement at s 1⁄4 13 TeV [6] All of these studies found the measured inclusive cross sections to be compatible with the SM predictions and set limits on the presence of anomalous TGCs. In the present analysis, WÆγ events are selected with one charged lepton (l), which is either an electron or muon, one neutrino (ν), and one photon (γ) in the final state. Interference between the LO WÆγ production diagrams results in a cross section that vanishes in specific phase space regions. This effect is known as a radiation amplitude zero (RAZ) [7–11].
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