Impact of QED radiative corrections on Parton Distribution Functions

Abstract: The level of precision achieved by the experimental measurements at the LHC requires the inclusion of higher order electroweak effects to the processes of $ pp $ scattering. In particular the photon-induced process $ \gamma\gamma \to \ell^+\ell^- $ make a significant contribution ($ \sim 10 \%$) to the dilepton invariant mass distribution. To evaluate the cross-section of this process one need to know the parton distribution function (PDF) of the photon in the proton $ \gamma (x,\mu^2) $. The aim of the current study is to investigate the impact of QED corrections on PDFs and describe the implementation of QED-modified evolution equations into beta release of new version of {\tt QCDNUM} program. The {\tt APPLGRID} interface to {\tt SANC} Monte Carlo generator for fast evaluation of photon-induced cross-section is also outlined. The results were cross-checked with {\tt partonevolution} program, {\tt MRST2004QED} PDF set and {\tt APFEL} program. The described developments are planned to include into {\tt HERAFitter} package and can be used to determine the photon PDF using new data from the LHC experiments.