Precision studies of Drell-Yan transverse momentum distributions and the polarisation angular coefficients in Z-boson decays with the ATLAS detector

The ATLAS collaboration has performed precision measurements sensitive to the transverse mo- mentum of the Z/γ∗ bosons, both directly through the transverse momentum of the dilepton pair and through the angular decorrelation as measured in the φ∗ observable. These measurements are sensitive to soft resummation effects and hard jet emissions for small and large momentum transfers, respectively, probing QCD in a unique way. The studies carried out with 20.3 fb−1 of data at a center-of-mass energy of 8 TeV probe a wide dilepton invariant mass region from 12 GeV to 150 GeV, both integrated and differential in the dilepton rapidity. The measurements are compared to a variety of resummation calculations and parton shower Monte Carlos at up to NNLO+NNLL as well as fixed order predictions at NNLO QCD including NLO electroweak corrections. The precision measurement of angular distributions of the Drell-Yan lepton pairs around the Z-boson mass peak provide a stringent test of the underlying QCD dynamic of the Z-boson production mechanisms through spin-correlation effects between initial and final state. A measurement is presented of the complete set of eight angular coefficients describing these distributions as determined from 20.3 fb−1 data collected with the ATLAS detector at a center-of- mass energy of 8 TeV. The measurements are carried out with a fine granularity in the Z-boson transverse momentum as well as three coarse Zrapidity intervals. The measurements are com- pared to precise theory calculations at NNLO in QCD and state-of-the-art MC generation at NLO in QCD. Strong discrimination power between different approaches of the QCD modeling and effects beyond NNLO are found.