Measurement of the transverse momentum and Øn∗ distributions of Drell–Yan lepton pairs in proton–proton collisions at √s = 8 TeV with the ATLAS detector

Distributions of transverse momentum pllTpTll and the related angular variable ϕ∗ηϕη∗ of DrellΓCoYan lepton pairs are measured in 20.3┬afb −1−1 of protonΓCoproton collisions at s√=8s=8 ┬aTeV with the ATLAS detector at the LHC. Measurements in electron-pair and muon-pair final states are corrected for detector effects and combined. Compared to previous measurements in protonΓCoproton collisions at s√=7s=7 ┬aTeV, these new measurements benefit from a larger data sample and improved control of systematic uncertainties. Measurements are performed in bins of lepton-pair mass above, around and below the Z-boson mass peak. The data are compared to predictions from perturbative and resummed QCD calculations. For values of ϕ∗η<1ϕη∗<1 the predictions from the Monte Carlo generator ResBos are generally consistent with the data within the theoretical uncertainties. However, at larger values of ϕ∗ηϕη∗ this is not the case. Monte Carlo generators based on the parton-shower approach are unable to describe the data over the full range of pllTpTll while the fixed-order prediction of Dynnlo falls below the data at high values of pllTpTll . ResBos and the parton-shower Monte Carlo generators provide a much better description of the evolution of the ϕ∗ηϕη∗ and pllTpTll distributions as a function of lepton-pair mass and rapidity than the basic shape of the data.