Measurement of exclusive γγ → +− production in proton–proton collisions at √s = 7 TeV with the ATLAS detector

Barton, Adam Edward and Beattie, Michael and Borissov, Guennadi and Bouhova-Thacker, Evelina Vassileva and Dearnaley, William and Fox, Harald and Grimm, Kathryn Ann Tschann and Henderson, Robert Charles William and Hughes, Gareth and Jones, Roger William Lewis and Kartvelishvili, Vakhtang and Long, Robin Eamonn and Love, Peter Allan and Maddocks, Harvey and Skinner, Malcolm and Smizanska, Maria and Walder, James William and Wharton, Andy (2015) Measurement of exclusive γγ → +− production in proton–proton collisions at √s = 7 TeV with the ATLAS detector. Physics Letters B, 749. pp. 242-261. ISSN 0370-2693

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 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 σexcl. 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, muon transverse momentum pT > 10 GeV and 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.