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
Author
Dr
Elizaveta Shabalina
(University of Gottingen)
