Photon Structure, as seen at HERA

At HERA, the electron-proton collider at DESY, Hamburg, the large flux of almost on-shell photons accompanying the lepton beam is being used to shed new light on the structure of the photon. Recent results are reviewed and discussed, with emphasis on those aspects of the photon's nature which should be understandable using perturbative QCD.Comment: 20 pages, latex, 10 figures appended as uuencoded file. Full postscript version including figures available at http://zow00.desy.de:8000/~butterwo/pubs.html#ke

The CEDAR Project

We describe the plans and objectives of the CEDAR project (Combined e-Science Data Analysis Resource for High Energy Physics) newly funded by the PPARC e-Science programme in the UK. CEDAR will combine the strengths of the well established and widely used HEPDATA database of HEP data and the innovative JetWeb data/Monte Carlo comparison facility, built on the HZTOOL package, and will exploit developing grid technology. The current status and future plans of both of these individual sub-projects within the CEDAR framework are described, showing how they will cohesively provide (a) an extensive archive of Reaction Data, (b) validation and tuning of Monte Carlo programs against these reaction data sets, and (c) a validated code repository for a wide range of HEP code such as parton distribution functions and other calculation codes used by particle physicists. Once established it is envisaged CEDAR will become an important Grid tool used by LHC experimentalists in their analyses and may well serve as a model in other branches of science where there is a need to compare data and complex simulations.Comment: 4 pages, 4 postscript figures, uses CHEP2004.cls. Presented at Computing in High-Energy Physics (CHEP'04), Interlaken, Switzerland, 27th September - 1st October 200

Photoproduction Processes in Polarized ep - Collisions at HERA

We study various conceivable photoproduction reactions in a polarized ep collider mode of HERA with respect to their sensitivity to the proton's polarized gluon distribution. A special emphasis is put on the `resolved' part of the cross sections which in principle opens the possibility to determine for the first time also the completely unknown parton content of longitudinally polarized photons. In the very promising case of dijet production we also investigate the impact of parton showering, hadronization and jet finding on the parton level results.Comment: 16 pages, LaTeX, 7 figures, uses epsfig, amssymb, and a41 (included) styles; Contribution to the proceedings of the 1997 workshop on 'Physics with Polarized Protons at HERA', Hamburg and Zeuthen, Germany, March-September 199