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)