Precision studies of Drell-Yan transverse momentum distributions and the polarisation angular coefficients in Z boson decays with the ATLAS detector (WG2)

Apr 13, 2016, 9:00 AM
20m
SR1 (DESY Hamburg)

SR1

DESY Hamburg

Electroweak Physics and Beyond the Standard Model WG2/WG3 joint session (QCD+EW)

Speaker

Aleksei Ezhilov (B.P. Konstantinov Petersburg Nuclear Physics Institute - PNPI)

Description

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 di-lepton 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 center-of-mass energy of 8TeV probe a wide di-lepton invariant mass region from 12 GeV to 150 GeV, both integrated and differential in the di-lepton 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 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 Z rapidity intervals. The measurements are compared 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

Primary author

Dr Elizaveta Shabalina (University of Gottingen)

Presentation materials