Measurement of the Transverse Momentum and ϕ[subscript η]* Distributions of Drell–Yan Lepton Pairs in Proton–proton Collisions at √s = 8 TeV with the ATLAS Detector

Abstract

Distributions of transverse momentum p[subscript T][superscript ℓℓ] and the related angular variable ϕ[subscript η]* of Drell–Yan lepton pairs are measured in 20.3fb ⁻¹ of proton–proton collisions at √ s = 8 TeV 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 proton–proton collisions at √ s = 7 TeV, 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[subscript η]* < 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[subscript η]* 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 p[subscript T][superscript ℓℓ] while the fixed-order prediction of Dynnlo falls below the data at high values of p[subscript T][superscript ℓℓ] . ResBos and the parton-shower Monte Carlo generators provide a much better description of the evolution of the ϕ[subscript η]* and p[subscript T][superscript ℓℓ] distributions as a function of lepton-pair mass and rapidity than the basic shape of the data.