Speaker
Description
Realizing the precision physics paradigm at the LHC requires the calculation of hard-scattering cross-sections which include perturbative QCD corrections up to (N)NNLO and electroweak corrections up to NLO. For consistency, parton distribution functions (PDFs) need to be provided with matching accuracy, which in the case of QED effects involves introducing the photon parton distribution of the proton, $x\gamma(x;Q)$. In this work, a novel determination of the photon PDF from fits to the recent ATLAS measurements of high-mass Drell-Yan production at $\sqrt{s}$ = 8 TeV has been presented. The analysis is performed using the xFitter framework which involves improvements both in the APFEL program, to account for NLO QED effects, and in the aMCfast interface to account for the photon-initiated contributions in the EW calculations within MadGraph5_aMC@NLO. The results of this work have been compared with other recent QED fits and determinations, finding in particular good agreement with the LUXqed and the HKR calculations within PDF uncertainties, in the kinematical range where the ATLAS DY measurement has sensitivity to $x\gamma(x;Q)$.
