Measurement of the transverse momentum and $\phi ^*_{\eta }$ distributions of Drell–Yan lepton pairs in proton–proton collisions at $\sqrt{s}=8$  TeV with the ATLAS detector

Distributions of transverse momentum $p_T^{\ell \ell }$ and the related angular variable $\phi ^*_\eta $ of DrellΓÇôYan lepton pairs are measured in 20.3┬áfb$^{-1}$ of protonΓÇôproton collisions at $\sqrt{s}=8$ ┬áTeV 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 protonΓÇôproton collisions at $\sqrt{s}=7$ ┬áTeV, 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 $\phi ^*_\eta < 1$ the predictions from the Monte Carlo generator ResBos are generally consistent with the data within the theoretical uncertainties. However, at larger values of $\phi ^*_\eta $ 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 $p_T^{\ell \ell }$ while the fixed-order prediction of Dynnlo falls below the data at high values of $p_T^{\ell \ell }$ . ResBos and the parton-shower Monte Carlo generators provide a much better description of the evolution of the $\phi ^*_\eta $ and $p_T^{\ell \ell }$ distributions as a function of lepton-pair mass and rapidity than the basic shape of the data.