Probing the photonic content of the proton using photon-induced dilepton production in p plus Pb collisions at the LHC

We propose a new experimental method to probe the photon parton distribution function inside the proton (photon PDF) at LHC energies. The method is based on the measurement of dilepton production from the gamma p -> l(+)l(-) + X reaction in proton-lead collisions. These experimental conditions guarantee a clean environment, both in terms of reconstruction of the final state and in terms of possible background. We first calculate the cross sections for this process with collinear photon PDFs, where we identify the optimal choice of the scale, in analogy to deep inelastic scattering kinematics. We then perform calculations including the transverse-momentum dependence of the probed photon. Finally, we estimate rates of the process for the existing LHC data samples.