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 σγγ→e+e-excl.=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, muon transverse momentum pT>10 GeV and pseudorapidity |η|<2.4, the cross-section is determined to be σγγ→μ+μ-excl.=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.

Aad, G., Abbott, B., Abdallah, J., Abdinov, O., Aben, R., Abolins, M., et al. (2015). Measurement of exclusive γγ→l+l- production in proton-proton collisions at sqrt(s)=7 TeV with the ATLAS detector. PHYSICS LETTERS. SECTION B, 749, 242-261 [10.1016/j.physletb.2015.07.069].

Measurement of exclusive γγ→l+l- production in proton-proton collisions at sqrt(s)=7 TeV with the ATLAS detector

F. Ceradini;B. Di Micco;R. Di Nardo;D. Orestano;F. Petrucci;D. Puddu;G. Salamanna;