Measurement of the <i>W</i>-boson angular coefficients and transverse momentum in <i>pp</i> collisions at √ s =13 TeV with the ATLAS detector

The angular distributions of Drell-Yan lepton pairs provide sensitive probes of the underlying dynamics of quantum chromodynamics (QCD) effects in vector-boson production. This paper presents for the first time the measurement of the full set of angular coefficients together with the differential cross-section as a function of the transverse momentum of the <i>W</i> boson, in the full phase space of the decay leptons. The measurements are performed separately for the W^- and W⁺ channels. The analysis uses proton-proton collision data recorded by the ATLAS experiment at the Large Hadron Collider in 2017 and 2018, during special low-luminosity runs with a reduced number of interactions per bunch crossings (pile-up). The data correspond to an integrated luminosity of 338 pb^-1 at a centre-of-mass energy of √ <i>s</i> =13 TeV. The low pile-up conditions enable an optimised reconstruction of the<i> W</i> boson transverse momentum. All results agree with theory predictions incorporating finite-order QCD corrections up to next-to-next-to-leading-order in the strong coupling constant, <i>α</i>_{<i>S </i>}.