Measurement of (Anti)deuteron and (Anti)proton Production in DIS at HERA

The first observation of (anti)deuterons in deep inelastic scattering at HERA has been made with the ZEUS detector at a centre-of-mass energy of 300-318 GeV using an integrated luminosity of 120 pb-1. The measurement was performed in the central rapidity region for transverse momentum per unit of mass in the range 0.3 \u3c pT / M \u3c 0.7. The particle rates have been extracted and interpreted in terms of the coalescence model. The (anti)deuteron production yield is smaller than the (anti)proton yield by approximately three orders of magnitude, consistent with the world measurements. © 2007 Elsevier B.V. All rights reserved

Diffractive Photoproduction of Dijets in ep Collisions at HERA

Diffractive photoproduction of dijets was measured with the ZEUS detector at the ep collider HERA using an integrated luminosity of 77.2 pb-1. The measurements were made in the kinematic range Q2 \u3c 1 GeV 2, 0.2

High-ET Dijet Photoproduction at HERA

The cross section for high-ET dijet production in photoproduction has been measured with the ZEUS detector at HERA using an integrated luminosity of 81.8pb-1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1GeV2 and a photon-proton center-of-mass energy in the range 14215GeV and pseudorapidity (with respect to the proton beam direction) requirements of -1\u3cηjet1,

Measurement of Open Beauty Production at HERA in the D \u3csup\u3e*\u3c/sup\u3eΜ Final State

The 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-1. Low transverse-momentum thresholds for the muon and D* 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. © Springer-Verlag Berlin Heidelberg 2007

Measurement of Azimuthal Asymmetries in Neutral Current Deep Inelastic Scattering at HERA

The distribution of the azimuthal angle of charged and neutral hadrons relative to the lepton plane has been studied for neutral current deep inelastic ep scattering using an integrated luminosity of 45 pb-1 taken with the ZEUS detector. The kinematic range is 10

Forward-Jet Production in Deep Inelastic ep Scattering at HERA

Forward jet cross sections have been measured in neutral current deep inelastic scattering at low Bjorken-x with the ZEUS detector at HERA using an integrated luminosity of 81.8 pb-1. Measurements are presented for inclusive forward jets as well as for forward jets accompanied by a dijet system. The explored phase space, with jet pseudorapidity up to 4.3 is expected to be particularly sensitive to the dynamics of QCD parton evolution at low x. The measurements are compared to fixed-order QCD calculations and to leading-order parton-shower Monte Carlo models. © 2007 Springer-Verlag / Società Italiana di Fisica

Bose-Einstein Correlations of Charged and Neutral Kaons in Deep Inelastic Scattering at HERA

Bose-Einstein correlations of charged and neutral kaons have been measured in e ± p deep inelastic scattering with an integrated luminosity of 121 pb -1 using the ZEUS detector at HERA. The two-particle correlation function was studied as a function of the four-momentum difference of the kaon pairs, Q 12 = sqrt(- (p 1 - p 2) 2), assuming a Gaussian shape for the particle source. The values of the radius of the production volume, r, and of the correlation strength, λ, were obtained for both neutral and charged kaons. The radii for charged and neutral kaons are similar and are consistent with those obtained at LEP. © 2007 Elsevier B.V. All rights reserved

Measurement of Neutral Current Cross Sections at High Bjorken-X with the ZEUS Detector at HERA

A new method is employed to measure the neutral current cross section up to Bjorken-x values of one with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb-1 for e+p collisions and 16.7 pb-1 for e-p collisions at √s = 318 GeV and 38.6 pb-1 for e+p collisions at √s = 300 GeV. Cross sections have been extracted for Q2 ≥648 GeV2 and are compared to predictions using different parton density functions. For the highest x bins, the data have a tendency to lie above the expectations using recent parton density function parametrizations. © Springer-Verlag Berlin Heidelberg 2007

Search for Stop Production in R-Parity-Violating Supersymmetry at HERA

A search for stop production in R-parity-violating supersymmetry has been performed in e+p interactions with the ZEUS detector at HERA, using an integrated luminosity of 65 pb-1. At HERA, the R-parity-violating coupling λ\u27 allows resonant squark production, e+d→̃ q. Since the lowest-mass squark state in most supersymmetry models is the light stop, ̃t, this search concentrated on production of ̃t, followed either by a direct R-parity-violating decay, or by the gauge decay to b̃x1+. No evidence for stop production was found and limits were set on λ\u27131 as a function of the stop mass in the framework of the minimal supersymmetric standard model. The results have also been interpreted in terms of constraints on the parameters of the minimal supergravity model. © Springer-Verlag Berlin Heidelberg 2007

Measurement of High- Q \u3csup\u3e2\u3c/sup\u3e Deep Inelastic Scattering Cross Sections with a Longitudinally Polarised Positron Beam at HERA

The cross sections for charged and neutral current deep inelastic scattering in e + p collisions with a longitudinally polarised positron beam have been measured using the ZEUS detector at HERA. The results, based on data corresponding to an integrated luminosity of 23.8 pb -1 at sqrt(s) = 318 GeV, are given for both e + p charged current and neutral current deep inelastic scattering for both positive and negative values of the longitudinal polarisation of the positron beam. Single differential cross sections are presented for the kinematic region Q 2 \u3e 200 GeV 2. The measured cross sections are compared to the predictions of the Standard Model. A fit to the data yields σ CC ( P e = - 1 ) = 7.4 ± 3.9 ( stat. ) ± 1.2 ( syst. ) pb, which is consistent within two standard deviations with the absence of right-handed charged currents in the Standard Model. © 2006 Elsevier B.V. All rights reserved