Professor Amanda Cooper-Sarkar

Abstract:

The J/ψ decay angular distributions have been measured in inelastic photo-production in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb-1. The range in photon-proton centre-of-mass energy, W, was 50 < W < 180 GeV. The J/ψ mesons were identified through their decay into muon pairs. The polar and azimuthal angles of the μ+ were measured in the J/ψ rest frame and compared to theoretical predictions at leading and next-to-leading order in QCD. © SISSA 2009.

Abstract:

Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb-1. The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e+p collision data with a scalar sum of the lepton transverse momenta above 100GeV while 1.94 ± 0.17 events are expected. Such events are not observed in e-p collisions for which 1.19 ± 0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions. © SISSA 2009.

Abstract:

The reduced cross sections for ep deep inelastic scattering have been measured with the ZEUS detector at HERA at three different centre-of-mass energies, 318, 251 and 225 GeV. From the cross sections, measured double differentially in Bjorken x and the virtuality, Q 2, the proton structure functions F L and F 2 have been extracted in the region 5 × 10 - 4 < x < 0.007 and 20 < Q 2 < 130 GeV 2. © 2009 Elsevier B.V.