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

Distributions of transverse momentum $$p_T^{\ell \ell }$$ and the related angular variable $$\phi ^*_\eta $$ of Drell–Yan lepton pairs are measured in 20.3 fb $$^{-1}$$ of proton–proton collisions at $$\sqrt{s}=8$$ 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 $$\sqrt{s}=7$$ 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 $$\phi ^*_\eta < 1$$ 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.

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