Diffractive Physics at HERA

Brief review of the diffractive physics at HERA, stressing QCD aspects.Comment: Contribution to the INPC98 proceeding, 5 pages, 6 figure

Progress and Problems in QCD - Report from the Hadronic Final States Working Group at DIS99

We present a summary of the Hadronic Final States parallel sessions of the DIS99 Workshop. Topics were presented over two days and included both theoretical and experimental talks. Recent progress in the understanding of QCD in deep inelastic scattering, e^+e^- collisions, and in gamma and p collisions was discussed.Comment: 15 pages, 22 figures, Latex, nbp.sty. To be published in the Proceedings of DIS'99, Zeuthen, Germany, 19-23 April 199

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

Structure function results from H1

New structure function results from H1 are presented. The measurements cover a huge kinematical range for Q^2, the four momentum transfer squared, from 0.35, GeV^2 to 30,000, GeV^2, and for Bjorken x between \sim 5\cdot 10^{-6} and 0.65. At Q^2>100, GeV^2, full HERA, I data have been analyzed. The data are compared with a new QCD analysis. The impact of the HERA, I data on the parton density functions is discussed.Comment: 8 page

Deep inelastic diffractive scattering at HERA

Recent high precision measurements of deep inelastic diffractive scattering at HERA are presented in an increased region of phase space. Current models for diffractive photon dissociation are compared to the data.Comment: 6 pages, 6 figures, talk presented at QCD03, Montpellier, France, July 2-9, 200

Forward pi^0-meson production at HERA

The production of high transverse momentum piz^0-mesons has been measured in deep-inelastic e-p scattering events at low Bjorken-$x$ taken with the H1 detector at HERA. The production of high p_T particles is strongly correlated to the emission of hard partons in QCD and is therefore sensitive to the dynamics of the strong interaction. For the first time the measurement of single particles has been extended to the region of small angles w.r.t. the proton remnant (forward region) and down to very low values of x ~ 5x10^-5. This region is expected to be particularly sensitive to QCD evolution effects in final states. Differential cross sections of inclusive pi^0-meson production have been measured as a function of Bjorken-x and the four-momentum transfer Q^2, and also as a function of the transverse momentum and the polar angle of the pi^0-mesons. A recent BFKL calculation and QCD models based on the DGLAP splitting functions are compared to the data. The best description of the data is achieved by the BFKL calculation.Comment: 3 pages, 2 figures, talk given on behalf of the H1 collaboration at DIS99, Zeuthe

Real and virtual photon structure from dijet events

Jet production in $ep$ collisions is sensitive to the partonic structure of photon. The latest measurements of dijet production from the H1 experiment provide new results of the gluon density of real photons at low $x$ and, for the first time, on the partonic density of virtual photons. Properties of the photon remnant were measured as a function of the hard scale defined by the $p_T$ of the jets. The comparison of dijet cross sections with the NLO QCD calculation shows the non-triviality of the concept of virtual photon structure.Comment: 4 pages, Latex with 4 ps figures, references for section 5 updated, Talk presented at DIS99 Workshop at Zeuthen, April 199

Jets in Deep Inelastic Scattering and High Energy Photoproduction at HERA

Recent results on jet production in neutral current deep inelastic scattering and high energy photoproduction at the HERA electron-proton-collider are briefly reviewed. The results are compared to QCD expectations in NLO and $\alpha_s$ determinations using these data are summarized.Comment: 12 pages, 10 figures, talk given at the 9th Adriatic Meeting "Particle Physics and the Universe" in Dubrovnik/Croatia, 4.-24.9.200

NRQCD Factorization and Quarkonium Production at Hadron-Hadron and ep Colliders

I review the NRQCD factorization approach for quarkonium production and compare its predictions with measurements in hadron-hadron and ep collisions.Comment: 6 pages, contribution to the proceedings of Charm 2010, IHEP, Beijing, October 21-24, 201

Experimental review of unpolarised nucleon structure functions

Recent results are reviewed on unpolarised structure functions from fixed target experiments at JLAB, NuTeV and from the HERA ep collider experiments H1 and ZEUS.Comment: Invited talk at the 10th International Conference on the Structure of Baryons (Baryons 2004), Palaiseau, France, 25-29 October 2004; 12 pages, 10 figure