The description of the structure of proton is fundamental in order to
describe the standard model processes at the LHC as well as for the searching
of New Physics. Quantum fluctuations imply the presence of photons and leptons
inside the proton, which admit a parton distribution function (PDF). Although
the lepton PDFs are expected to be small, its presence opens new production
mechanisms. In order to explore the lepton - induced processes at the LHC, a
precise determination of the leptonic content of the proton is needed. In this
paper we propose to constrain the content of charged leptons inside the proton
through the study of the QED Compton scattering in ultraperipheral proton -
nucleus collisions at the LHC. We estimate the total cross sections and
associated distributions considering different models for the lepton PDFs and
distinct lepton flavours. We demonstrate that a future experimental analysis of
this process is feasible and that it can be used to constrain the content of
electrons, muons and taus inside the proton.Comment: 10 pages, 3 figures, 1 table. Improved version to be published in PR