Measurement of Electroweak W Boson Production via Vector‐Boson Fusion in Proton–Proton Collisions at √s = 13 TeV with the CMS Detector

This work reports a precise measurement of the electroweak production of a W boson in association with two jets (pp → W jj) at √s = 13 TeV, using the full Run II dataset recorded by the CMS experiment at the CERN Large Hadron Collider (LHC), corresponding to an integrated luminosity of 138 fb−1. The process, characterised by the vector boson fusion (VBF) topology, provides a sensitive probe of the gauge structure of the Standard Model (SM) and of possible deviations from it. The first part of the work establishes the theoretical and statistical foundations of the measurement, introducing the mathematical structure of the SM and its Effective Field Theory (EFT) extension, together with the likelihood based methods used for parameter inference. A brief description of the LHC and the CMS detector follows, outlining the experimental environment that enables precision measurements of electroweak processes. The analysis targets single-lepton final states (W → ℓνjj, ℓ = e, µ) consistent with the VBF topology. Particular emphasis is placed on the reliability of simulated samples and on the data-driven corrections applied to improve their modelling. A deep neural network classifier enhances the separation between electroweak and QCD components, and the signal strength is extracted with a simultaneous binned profile-likelihood fit, yielding an expected total uncertainty of 10%. Fiducial and differential measurements are also performed within a restricted particle-level phase space to reduce model dependence. Unfolded cross sections are extracted as functions of several generator-level observables, and an innovative unfolding strategy based on multiclass neural networks is compared to a traditional approach relying on reconstructed observables only. Finally, the measurement is interpreted in the context of the Standard Model Effective Field Theory, providing sensitivity to higher-dimensional operators that modify electroweak interactions. An independent EFT interpretation of the W jj process is followed by a global CMS combination including all major bosonic channels, in which each input uses fully simulated EFT signal samples with their associated experimental and theoretical uncertainties. This combined result offers a coherent picture of the electroweak sector within the EFT framework and delivers globally consistent constraints on potential deviations from the Standard Model.