Professor Amanda Cooper-Sarkar

Abstract:

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. © SISSA 2009.

Abstract:

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||)D* /2Ejet, where E is the energy of the D * meson and p|| is the longitudinal momentum of the D * meson relative to the axis of the associated jet of energy Ejet. Jets were reconstructed using the kT 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. © SISSA 2009.