Production of excited charm and charm-strange mesons at HERA
European Physical Journal C 60:1 (2009) 25-45
Abstract:
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.Search for events with an isolated lepton and missing transverse momentum and a measurement of W production at HERA
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 672:2 (2009) 106-115
Abstract:
A search for events with an isolated high-energy lepton and large missing transverse momentum has been performed with the ZEUS detector at HERA using a total integrated luminosity of 504 pb-1. The results agree well with Standard Model predictions. The cross section for production of single W bosons in electron-proton collisions with unpolarised electrons is measured to be 0.89-0.22+0.25 (stat.) ± 0.10 (syst.) pb. © 2009 Elsevier B.V.A measurement of the Q2, W and t dependences of deeply virtual Compton scattering at HERA
Journal of High Energy Physics 2009:5 (2009)
Abstract:
Deeply virtual Compton scattering, γ*p→γp has been measured in e+p collisions at HERA with the ZEUS detector using an integrated luminosity of 61.1 pb-1. Cross sections are presented as a function of the photon virtuality, Q2, and photon-proton centre-of-mass energy, W, for a wide region of the phase space, Q2 > 1.5GeV2 and 40 < W < 170GeV. A subsample of events in which the scattered proton is measured in the leading proton spectrometer, corresponding to an integrated luminosity of 31.3 pb-1, is used for the first direct measurement of the differential cross section as a function of t, where t is the square of the four-momentum transfer at the proton vertex. © SISSA 2009.Measurement of beauty photoproduction using decays into muons in dijet events at HERA
Journal of High Energy Physics 2009:4 (2009)
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.Measurement of the charm fragmentation function in D* photoproduction at HERA
Journal of High Energy Physics 2009:4 (2009)