Measurement of angular correlations in Drell–Yan lepton pairs to probe Z / γ ? boson transverse momentum at s = 7 TeV with the ATLAS detector

摘要

A measurement of angular correlations in Drell–Yan lepton pairs via the ? η ? observable is presented. This variable probes the same physics as the Z / γ ? boson transverse momentum with a better experimental resolution. The Z / γ ? → e + e ? and Z / γ ? → μ + μ ? decays produced in proton–proton collisions at a centre-of-mass energy of s = 7 ? TeV are used. The data were collected with the ATLAS detector at the LHC and correspond to an integrated luminosity of 4.6 fb ?1 . Normalised differential cross sections as a function of ? η ? are measured separately for electron and muon decay channels. These channels are then combined for improved accuracy. The cross section is also measured double differentially as a function of ? η ? for three independent bins of the Z boson rapidity. The results are compared to QCD calculations and to predictions from different Monte Carlo event generators. The data are reasonably well described, in all measured Z boson rapidity regions, by resummed QCD predictions combined with fixed-order perturbative QCD calculations or by some Monte Carlo event generators. The measurement precision is typically better by one order of magnitude than present theoretical uncertainties.