86 research outputs found

    Erratum: Measurement of D^{∗±} production in deep inelastic scattering at HERA

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    The ZEUS collaborationIn the analysis for our paper on D* production, the beauty contribution was erroneously subtracted twice in the extraction of the reduced cross sections. This affected tables 9 and 10 as well as figures 9 and 10 that are reproduced here in a corrected version. The kinematical acceptances shown in the last colum of table 10 have been also corrected since they were calculated with a different value for the charm fragmentation fraction than what was used in the rest of the analysis and reported in the text. A misprint was found in table 7: the value in the third column at four rows from the bottom should read 49.8, not 59.8. Finally, one of the authors was missing from the author list: C. Uribe-Estrada (Department of Physics, University of Oxford, United Kingdom).Article funded by SCOAP

    Events with an isolated lepton and missing transverse momentum and measurement of W production at HERA

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    Events with high energy isolated electrons, muons or tau leptons and missing transverse momentum are studied using the full e ± p data sample collected by the H1 experiment at HERA, corresponding to an integrated luminosity of 474 pb -1. Within the Standard Model, events with isolated leptons and missing transverse momentum mainly originate from the production of single W bosons. The total single W boson production cross section is measured as 1.14±0.25 (stat.)±0.14 (sys.) pb, in agreement with the Standard Model expectation. The data are also used to establish limits on the WW γ gauge couplings and for a measurement of the W boson polarisation

    A measurement of the Q(2), W and t dependences of deeply virtual Compton scattering at HERA

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    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 high-Q (2) charged current deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA

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    Measurements of the cross sections for charged current deep inelastic scattering in e+p collisions with a longitudinally polarised positron beam are presented. The measurements are based on a data sample with an integrated luminosity of 132 pb-1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is presented at positive and negative values of the longitudinal polarisation of the positron beams. The single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2>200 GeV2. The reduced cross-section σ̃ is presented in the kinematic range 200&lt;Q2&lt;60000 GeV2 and 0.006&lt;x&lt;0.562. The measurements agree well with the predictions of the Standard Model. The results are used to determine a lower limit on the mass of a hypothetical right-handed W boson. © 2010 The Author(s)

    Photoproduction of isolated photons, inclusively and with a jet, at HERA

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    The photoproduction of isolated photons, both inclusive and together with a jet, has been measured with the ZEUS detector at HERA using an integrated luminosity of 374 pb−1. Differential cross sections are presented in the isolated-photon transverse-energy and pseudorapidity ranges and −0.7&#60;ηγ&#60;0.9, and for jet transverse-energy and pseudorapidity ranges and −1.5&#60;ηjet&#60;1.8, for exchanged-photon virtualities Q2&#60;1 GeV2. Differential cross sections are also presented for inclusive isolated-photon production as functions of the transverse energy and pseudorapidity of the photon. Higher-order theoretical calculations are compared to the results

    Measurement of Inelastic J/ψJ/\psi and ψ\psi^{\prime} Photoproduction at HERA

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    The cross sections for inelastic photoproduction of J/ψ and ψ′ mesons have been measured in epcollisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb&lt;sup&gt;−1&lt;/sup&gt; collected in the period 1996–2007. The ψ′ to J/ψ cross section ratio was measured in the range 0.55 &lt; z&lt; 0.9 and 60 &lt; W &lt; 190 GeV as a function of &lt;i&gt;W, z&lt;/i&gt; and &lt;i&gt;p T&lt;/i&gt; . Here W denotes the photon-proton centre-of-mass energy, &lt;i&gt;z&lt;/i&gt; is the fraction of the incident photon energy carried by the meson and &lt;i&gt;p T&lt;/i&gt; is the transverse momentum of the meson with respect to the beam axis. The J/ψ cross sections were measured for 0.1 &lt; &lt;i&gt;z&lt;/i&gt; &lt; 0.9, 60 &lt; W &lt; 240 GeV and &lt;i&gt;p T&lt;/i&gt;  &gt; 1 GeV. Theoretical predictions within the non-relativistic QCD framework including NLO colour-singlet and colour-octet contributions were compared to the data, as were predictions based on the &lt;i&gt;k T -&lt;/i&gt; factorisation approach

    Further studies of the photoproduction of isolated photons with a jet at HERA

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    In this extended analysis using the ZEUS detector at HERA, the photoproduction of isolated photons together with a jet is measured for different ranges of the fractional photon energy, x meas γ , contributing to the photon-jet final state. Cross sections are evaluated in the photon transverse-energy and pseudorapidity ranges 6 &#60; Eγ T &#60; 15 GeV and −0.7 &#60; ηγ &#60; 0.9, and for jet transverse-energy and pseudorapidity ranges 4 &#60; Ejet T &#60; 35 GeV and −1.5 &#60; ηjet &#60; 1.8, for an integrated luminosity of 374 pb−1 . The kinematic observables studied comprise the transverse energy and pseudorapidity of the photon and the jet, the azimuthal difference between them, the fraction of proton energy taking part in the interaction, and the difference between the pseudorapidities of the photon and the jet. Higher-order theoretical calculations are compared to the results

    Exclusive photoproduction of gamma mesons at HERA

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    The exclusive photoproduction reaction γ p → Υ{hooked} p has been studied with the ZEUS experiment in ep collisions at HERA using an integrated luminosity of 468 pb -1. The measurement covers the kinematic range 60 < W < 220 GeV and Q 2 < 1   GeV 2, where W is the photon-proton centre-of-mass energy and Q 2 is the photon virtuality. These results, which represent the analysis of the full ZEUS data sample for this channel, are compared to predictions based on perturbative QCD. © 2009 Elsevier B.V

    Deep inelastic cross-section measurements at largeywith the ZEUS detector at HERA

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    The reduced cross sections for e+p deep inelastic scattering have been measured with the ZEUS detector at HERA at three different center-of-mass energies, 318, 251 and 225 GeV. The cross sections, measured double differentially in Bjorken x and the virtuality, Q2, were obtained in the region 0.13&#8804;y&#8804;0.75, where y denotes the inelasticity and 5&#8804;Q2&#8804;110  GeV2. The proton structure functions F2 and FL were extracted from the measured cross sections
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