Parton distributions with QED corrections

Abstract

We present a set of parton distribution functions (PDFs), based on the NNPDF2.3 set, which includes a photon PDF, and QED contributions to parton evolution. We describe the implementation of the combined QCD+QED evolution in the NNPDF framework. We then provide a first determination of the full set of PDFs based on deep-inelastic scattering data and LHC data for W and Z/gamma* Drell-Yan production, using leading-order QED and NLO or NNLO QCD. We compare the ensuing NNPDF2.3QED PDF set to the older MRST2004QED set. We perform a preliminary investigation of the phenomenological implications of NNPDF2.3QED: specifically, photon-induced corrections to direct photon production at HERA, and high-mass dilepton and W pair production at the LHC.

Comments: 38 pages, 27 figures. Final version, to be published in Nucl. Phys. B. Several corrections and improvements, in particular Fig.5 added, Fig.2, Fig. 6 and Fig.8 improved, Fig.21 corrected