Measurement of exclusive ɣɣ→l+l- production in proton-proton collisions at √s=7 TeV with the ATLAS detector

Abstract

This Letter reports a measurement of the exclusive γγ→ + −( =e,μ) cross-section in proton–proton collisions at a centre-of-mass energy of 7TeVby the ATLAS experiment at the LHC, based on an inte-grated luminosity of 4.6fb−1. For the electron or muon pairs satisfying exclusive selection criteria, a fit to the dilepton acoplanarity distribution is used to extract the fiducial cross-sections. The cross-section in the electron channel is determined to be σexcl.γγ→e+e−=0.428±0.035(stat.)±0.018(syst.)pbfor a phase–space region with invariant mass of the electron pairs greater than 24GeV, in which both electrons have transverse momentum pT>12GeVand pseudorapidity |η| <2.4. For muon pairs with invariant mass greater than 20GeV, muon transverse momentum pT>10GeVand pseudorapidity |η| <2.4, the cross-section is determined to be σexcl.γγ→μ+μ−=0.628±0.032(stat.)±0.021(syst.)pb. When proton absorptive effects due to the finite size of the proton are taken into account in the theory calculation, the measured cross-sections are found to be consistent with the theory prediction.