Professor Claire Gwenlan

Abstract:

Inclusive jet differential cross sections have been measured in neutral current deep inelastic e +p scattering for boson virtualities Q 2 > 125 GeV 2. The data were taken using the ZEUS detector at HERA and correspond to an integrated luminosity of 38.6 pb -1. Jets were identified in the Breit frame using the longitudinally invariant k T cluster algorithm. Measurements of differential inclusive jet cross sections are presented as functions of jet transverse energy (E BT.jet), jet pseudorapidity and Q 2, for jets with E BT.jet > 8 GeV. Next-to-leading-order QCD calculations agree well with the measurements both at high Q 2 and high E BT.jet. The value of α s(M z), determined from an analysis of dσ/dQ 2 for Q 2 > 500 GeV 2, is α s(M Z=0.1212±0.0017 (stat.) +0.0023-0.0031 (syst.) +0.0028-0.0027(th.). © 2002 Elsevier Science B.V. All rights reserved.

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.