4 research outputs found
Measurement of J/ helicity distributions in inelastic photoproduction at HERA
The decay angular distributions have been measured in inelastic
photoproduction in collisions with the ZEUS detector at HERA, using an
integrated luminosity of 468 . The range in photon-proton
centre-of-mass energy, , was 50 180 . The mesons were
identified through their decay into muon pairs. The polar and azimuthal angles
of the were measured in the rest frame and compared to
theoretical predictions at leading and next-to-leading order in QCD.Comment: 15 page
Residential fieldwork: contributions to school science from a five-year initiative for inner-city students in the UK
The production of excited charm, D 1(2420)0 and D 2* (2460)0, and charm-strange, D s1(2536)±, mesons in ep collisions was measured with the ZEUS detector at HERA using an integrated luminosity of 126 pb -1. Masses, widths and helicity parameters were determined. The measured yields were converted to the rates of c quarks hadronising as a given excited charm meson and to the ratios of the dominant D 2* (2460)0 and D s1(2536) ± branching fractions. A search for the radially excited charm meson, D *(2640)±, was also performed. The results are compared with those measured previously and with theoretical expectations. © 2009 Springer-Verlag / Società Italiana di Fisica
Measurement of the charm fragmentation function in photoproduction at HERA
The charm fragmentation function has been measured in D* photoproduction with the ZEUS detector at HERA using an integrated luminosity of 120 pb(-1). The fragmentation function is measured versus z = (E + p(parallel to))(D)* / 2E(jet), where E is the energy of the D* meson and p(parallel to) is the longitudinal momentum of the D* meson relative to the axis of the associated jet of energy E(jet). Jets were reconstructed using the k(T) clustering algorithm and required to have transverse energy larger than 9GeV. The D* meson associated with the jet was required to have a transverse momentum larger than 2GeV. The measured function is compared to different fragmentation models incorporated in leading-logarithm Monte Carlo simulations and in a next-to-leading-order QCD calculation. The free parameters in each fragmentation model are fitted to the data. The extracted parameters and the function itself are compared to measurements from e(+)e(-) experiments
Measurement of Beauty Photoproduction using Decays into Muons in Dijet Events at HERA
Beauty photoproduction in dijet events has been measured at HERA with the ZEUS detector using an integrated luminosity of 126 pb(-1). Beauty was identified in events with a muon in the final state by using the transverse momentum of the muon relative to the closest jet. Lifetime information from the silicon vertex detector was also used; the impact parameter of the muon with respect to the primary vertex was exploited to discriminate between signal and background. Cross sections for beauty production as a function of the muon and the jet variables as well as dijet correlations are compared to QCD predictions and to previous measurements. The data are well described by predictions from next-to-leading-order QCD