102 research outputs found
The study of D and D meson production in deep inelastic scattering at HERA II with the ZEUS detector.
No full textInstalled in 2000/2001, the ZEUS micro vertex detector provided the capability to reconstruct secondary vertices displaced from the primary by distances of the order 100 pm. In order to be useful for tagging heavy flavour mesons the micro vertex detector was aligned with a combination of tracks from cosmic events and ep events in the HERA collider. This thesis presents measurements of and D meson production obtained with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb-1. The measurements cover the kinematic range 5 < Q2 < 1000 GeV2, 0.02 < y < 0.7, 1.5 < p{dollar} < 15 GeV and 11 < 1.6. Combinatorial background to the D meson signals is reduced by using the ZEUS micro vertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading order QCD which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open charm contribution, F2ca, to the proton structure function, F2
The Study of and Meson Production in Deep Inelastic Scattering at HERA II with the ZEUS Detector
No full textDiffractive photoproduction of D*(+/-) (2010) at HERA
No full textDiffractive photoproduction of D*±(2010) mesons was measured with the ZEUS detector at the ep collider HERA, using an integrated luminosity of 78.6 pb-1. The D* mesons were reconstructed in the kinematic range: transverse momentum pT(D*) > 1.9 GeV and pseudorapidity |η(D*)|<1.6, using the decay D*+→D0π+s followed by D0→K-π+(+c.c.). Diffractive events were identified by a large gap in pseudorapidity between the produced hadronic state and the outgoing proton. Cross sections are reported for photon-proton centre-of-mass energies in the range 130 < W < 300 GeV and for photon virtualities Q2 < 1 GeV2, in two ranges of the Pomeron fractional momentum xIP<0.035 and xIP<0.01. The relative contribution of diffractive events to the inclusive D*±(2010) photoproduction cross section is about 6%. The data are in agreement with perturbative QCD calculations based on various parameterisations of diffractive parton distribution functions. The results are consistent with diffractive QCD factorisation. © Springer-Verlag Berlin Heidelberg 2007
Measurement of D ± and D 0 production in deep inelastic scattering using a lifetime tag at HERA
No full textThe production of D <sup>±</sup>- and D <sup>0</sup>-mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb<sup>−1</sup>. The measurements cover the kinematic range 5<Q <sup>2</sup><1000 GeV<sup>2</sup>, 0.02<y<0.7, 1.5<<sub>p</sub><sub>T</sub><sup>D</sup> <15 GeV and |η <sup>D</sup> |<1.6. Combinatorial background to the D-meson signals is reduced by using the ZEUS microvertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading-order QCD, which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open-charm contribution, F<sub>2</sub><sup>cc</sup> , to the proton structure function, F <sub>2</sub>
Measurement of D-*+/- meson production in e(+/-)p scattering at low Q(2)
No full textThe production of D* ± (2010) mesons in e± p scattering in the range of exchanged photon virtuality 0.05 < Q2 < 0.7 GeV2 has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. The decay channels D* + → D0 π+ with D0 → K- π+ and corresponding antiparticle decay were used to identify D* mesons and the ZEUS beampipe calorimeter was used to identify the scattered electron. Differential D* cross sections as functions of Q2, inelasticity, y, transverse momentum of the D* meson, pT (D*), and pseudorapidity of the D* meson, η (D*), have been measured in the kinematic region 0.02 < y < 0.85, 1.5 < pT (D*) < 9.0 GeV and | η (D*) | < 1.5. The measured differential cross sections are in agreement with two different NLO QCD calculations. The cross sections are also compared to previous ZEUS measurements in the photoproduction and DIS regimes. © 2007 Elsevier B.V. All rights reserved
Measurement of the charm fragmentation function in D* photoproduction at HERA
No full textThe 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
Production, Stability and Biodiversity of North Island New Zealand Kill Pastures
No full textThe relationship between pasture biomass and pasture stability with species diversity was derived for two low fertility, hill land sites. At one site, pasture production increased with an increased number of species contributing to biomass. The coefficient of variation in biomass, however, decreased with higher numbers of species. At a second site, pasture biomass was also found to increase with increasing species diversity, but the relationship between yield stability and species diversity was not as strong as at the first site. This suggested there were other factors that influenced the stability of pastures, which could include the substitution effect between species or the greater contribution of particular species to yield and stability
Measurement of open beauty production at HERA in the D* mu final state
No full textThe production of beauty quarks with a D and a muon in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb<sup>-1</sup>. Low transverse-momentum thresholds for the muon and D<sup>*</sup> meson allow for a measurement of beauty production closer to the production threshold than previous measurements. The beauty signal was extracted using the charge correlations and angular distributions of the muon with respect to the D* meson. Cross sections for photoproduction and deep inelastic scattering are somewhat higher than, but compatible with, next-to-leading-order QCD predictions, and compatible with other measurements
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