Speaker
Konstantinos Bachas
(INFN Lecce)
Description
The angular distributions of Drell-Yan charged lepton pairs in the vicinity of the Z-boson mass peak probe the underlying QCD dynamics of Z-boson production. This talk presents measurements from ATLAS and CMS collaborations on the set of angular coefficients A0-Α7 describing these distributions using pp collisions at √s=8 TeV at the LHC. The measurements are compared to the QCD predictions at leading order, next-to-leading order, and next-to-next-to-leading order in perturbation theory. Drell–Yan charged lepton pairs in addition allow the transverse momentum of Z/γ∗ bosons, pT(ll) to be measured. The latter requires a precise understanding of the pT calibration and resolution of the final-state leptons. To minimize the impact of systematic uncertainties, the φ* observable derived from the angles subtended by the leptons is introduced. Its resolution is significantly better than that of pT(ll) and therefore it can be used as an alternative probe of pT(ll). Finally, the angular distributions of charged leptons and in particular the angular variable cosθ∗ between the outgoing lepton and the incoming quark in the Collins–Soper frame is useful for the measurement of the forward-backward asymmetry AFB in the production of Drell–Yan lepton pairs. In turn, measurements of AFB are used to extract the effective weak mixing angle. In this talk, measurements from ATLAS, CMS and LHCb experiments on φ*, cosθ* and AFB are presented at √s = 7,8 and 13 TeV.
Primary author
Konstantinos Bachas
(INFN Lecce)
