Analysis of Rapidity Gap Cuts in Diffractive DIS

The requirement of a large pseudo-rapidity gap to select diffractive DIS events at HERA restricts the kinematically accessible region of phase space for a significant range of $Q^2$, $\beta$ and \xpom. Consequences of this include a breakdown of \xpom-factorization in large rapidity gap diffractive samples and an enhancement in the relative contribution of quark-antiquark-gluon processes over dijet processes in the diffractive DIS sample.Comment: LaTeX, 3 pages, 2 figures in PS files, uses npb.sty. Contribution to the Proceedings of the 7th International Workshop on Deep Inelastic Scattering and QCD, DIS99, DESY-Zeuthen, April 1999; Nucl. Phys. B (Proc. Suppl.

Measurement of Feynman-x Spectra of Photons and Neutrons in the Very Forward Direction in Deep-Inelastic Scattering at HERA

Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic $ep$ scattering at HERA are presented as a function of the Feynman variable $x_F$ and of the centre-of-mass energy of the virtual photon-proton system $W$. The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of $131 \mathrm{pb}^{-1}$. The measurement is restricted to photons and neutrons in the pseudorapidity range $\eta>7.9$ and covers the range of negative four momentum transfer squared at the positron vertex $6<Q^2<100$ GeV$^2$, of inelasticity $0.05<y<0.6$ and of $70<W<245$GeV. To test the Feynman scaling hypothesis the $W$ dependence of the $x_F$ dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections.Comment: 30 pages, 5 tables, 10 figures, submitted to EPJ

Issues on NLO pQCD Programs

This paper summarizes a talk presented at the Durham HERA '98 Workshop. We compare the features that are available in NLO pQCD programs and demonstrate that understanding where in phase space NLO calculations are accurate is vital for extracting information from measurements at the HERA experiments.Comment: 3 page