ATLAS

Abstract:

Diffractive production of D*±(2010) mesons in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 44.3 pb-1. Diffractive charm production is identified by the presence of a large rapidity gap in the final state of events in which a D*±(2010) meson is reconstructed in the decay channel D*+ → (D0 → K-π+)πs+ (+ charge conjugate). Differential cross sections when compared with theoretical predictions indicate the importance of gluons in such diffractive interactions. © 2002 Elsevier Science B.V. All rights reserved.

Abstract:

Cross-sections for the photoproduction of events containing four high-ET jets have been measured with the ZEUS detector using an integrated luminosity of 38.7 pb-1. At low invariant mass of the four-jet system, m4J, the observed event distributions are sensitive to the underlying event model. The inclusion of multi-parton interactions in Monte Carlo simulations lead to a significantly better description of the data. For m4J > 50 GeV the data is adequately described by models with no simulation of an underlying event, suggesting that this is a kinematic region suitable for comparison with perturbative QCD calculations.

Abstract:

A discussion is presented of the manner in which uncertainties in parton distributions and related quantities are determined. One of the central problems is the criteria used to judge what variation of the parameters describing a set of partons is acceptable within the context of a global fit. Various ways of addressing this question are outlined.

Abstract:

A summary of the experimental and theoretical presentations in the Structure Function Working Group on the proton and photon unpolarized structure functions is given.