Combined HERA Deep Inelastic Scattering Data and NLO QCD Fits

Previously published data on inclusive neutral and charged current e+p and e-p deep inelastic scattering from HERA have been combined. The new, model-independent method of combining the measured cross sections takes full account of correlated systematics in a coherent way, leading to significantly reduced uncertainties in the combined measurement across the (x, Q^2) plane. The combined cross section data have been used as the sole input for a new next-to-leading order QCD fit to extract the parton distribution functions (PDFs) of the proton. The PDFs extracted have greatly reduced experimental uncertainties, compared to separate QCD analyses on data from H1 and ZEUS. Model uncertainties, including those arising from the parameterisation dependence, have also been carefully considered. The resulting HERA PDFs have impressive precision.Comment: 11 pages, 6 figures, prepared for the proceedings of the Ringberg Workshop on "New Trends in HERA Physics 2008", Ringberg Castle, Tegernsee, Oct 5-10, 200

Deuteron Structure Functions in the Context of Few-Body Physics

Few-body systems offer a unique challenge to those interested in deep inelastic scattering. Using the deuteron as the simplest and most easily solvable nuclear system we review the main physics issues in the valence and sea quark regimes. For the former the key issue is the understanding of Fermi motion and binding corrections, and our ability to extract the ratio F_2n/F_2p as x -> 1. The most recent analysis of deuteron data for F_2n/F_2p is consistent with perturbative QCD, but inconsistent with the assumptions common to all standard parton distribution fits. This should be taken into account in calculating event rates at HERA --- especially at large x and Q^2. The extraction of g_1n also presents an opportunity to refine the description of nuclear effects in spin-dependent structure functions. In the region of small x one must correct for shadowing and meson exchange current effects in order to explore the flavor structure of sea, which is, in turn, deeply related to the chiral structure of the nucleon.Comment: 20 pages, 7 postscript figures. Invited talk at the 15th Int. Conf. on Few-Body Problems in Physics, Groningen, The Netherlands, 22-26 July, 199