Precision studies of Drell-Yan pT distributions and polarization angular coefficients in Z boson decays with the ATLAS detector at 8 TeV

The ATLAS collaboration has performed precision measurements sensitive to the transverse momentum of the Z/gamma* bosons, both directly through the transverse momentum of the di­lepton pair and through the angular decorrelation as measured in the phi* 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 of data at a center­of­mass energy of 8TeV 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 Drell­Yan lepton pairs around the Z­boson mass peak provide a stringent test of the underlying QCD dynamic of the Z­boson production mechanisms through spin­correlation 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 data collected with the ATLAS detector at a center­of­mass energy of 8 TeV. The measurements are carried out with a fine granularity in the Z boson transverse momentum as well as three coarse Z rapidity intervals. The measurements are compared to precise theory calculations at NNLO in QCD and state­of­the­art MC generation at NLO in QCD as well as resummation calculations at up to NNLO+NNLL. Strong discrimination power between different approaches of the QCD modeling and effects beyond NNLO are found.