CERN-LHC. This Letter reports a measurement of the exclusive
γγ→ℓ+ℓ−(ℓ=e, μ) cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV by the ATLAS experiment at the LHC, based on an integrated luminosity of 4.6 fb−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 σ excl. γγ→e+e−=0.428 ± 0.035 (stat.) ± 0.018 (syst.) pb for a phase-space region with invariant mass of the electron pairs greater than 24 GeV, in which both electrons have transverse momentum pT>12 GeV and pseudorapidity |η|<2.4. For muon pairs with invariant mass greater than 20 GeV, muons transverse momentum pT >10 GeV
pT>10 GeV and pseudorapidity |η|<2.4, the cross-section is determined to be σ excl. γγ→μ+μ−=0.628 ± 0.032 (stat.) ± 0.021 (syst.) pb. When proton absorptive effects due to finite proton size are taken into account in the theory calculation, the measured cross-sections are found to be consistent with the prediction.
|Date made available||4 Jan 2015|