Sensitivity to exclusive WW production in photon scattering at the High Luminosity LHC

The prospects of measuring the process γγ→W+W− with the ATLAS detector during the high luminosity phase of the Large Hadron Collider (HL-LHC) with a centre-of-mass energy of 14 TeV and an integrated luminosity of 3000 fb−1 are studied. The opposite-flavour, opposite-sign fully leptonic final state is considered. The precision of the inclusive cross-section measurement in the fiducial volume is expected to be slightly improved relative to the one obtained in Run 2 measurement if the track transverse-momentum (pT) threshold can be maintained at 500MeV and assuming a systematic uncertainty of ± 12% on the background yield. This study compares baseline HL-LHC track reconstruction to low-pT tracking and finds that low-pT tracking is an essential research and development area for exclusive analyses at the HL-LHC. It also demonstrates that reducing background modelling uncertainties will be important in order to benefit from improvements in statistical precision. A differential analysis in dilepton mass shows that the sensitivity will be improved in the high-mass region with respect to the Run 2 analysis, opening up avenues for improved limits on anomalous gauge couplings and effective field theory fits in this region.