Measurement of the cross-section for Z → e+e- production in pp collisions at $\sqrt{s}=7$ TeV

Abstract

A bstract A measurement of the cross-section for pp → Z → e + e − is presented using data at $\sqrt{s}=7$ TeV corresponding to an integrated luminosity of 0.94 fb −1 . The process is measured within the kinematic acceptance p T > 20 GeV/ c and 2 < η < 4.5 for the daughter electrons and dielectron invariant mass in the range 60–120 GeV/ c 2 . The cross-section is determined to be $\sigma \left( {\mathrm{pp}\to \mathrm{Z}\to {{\mathrm{e}}^{+}}{{\mathrm{e}}^{-}}} \right)=76.0\pm 0.8\pm 2.0\pm 2.6\;\mathrm{pb}$ where the first uncertainty is statistical, the second is systematic and the third is the uncertainty in the luminosity. The measurement is performed as a function of Z rapidity and as a function of an angular variable which is closely related to the Z transverse momentum. The results are compared with previous LHCb measurements and with theoretical predictions from QCD.