Constraining the photon flux in two-photon processes at the LHC

Abstract

In this paper we propose the study of the $W^+W^-$ and $\mu^+\mu^-$ production by two-photon interactions in $pp$ collisions at LHC energies to constrain the photon flux associated to an ultrarelativistic proton. We consider the current parametrizations for the photon distribution of the proton and estimate the effective photon - photon luminosities for elastic, semielastic and inelastic processes. Moreover, we present predictions for the rapidity and invariant mass distributions for the two-photon production of $W^+W^-$ and $\mu^+\mu^-$ in $\gamma \gamma$ interactions at LHC energies. We demonstrate that the semielastic and inelastic predictions are strongly dependent on the description of the inelastic photon flux, and that the relative contribution of the different processes depends on the invariant mass of the final state. Our results implies that a dedicated experimental analysis of the two-photon production of $W^+W^-$ and $\mu^+\mu^-$ with the tagging of one of the protons in the final state can be useful to constrain the magnitude of the inelastic component of the photon distribution.