Inclusive-jet Photoproduction at HERA and Determination of α \u3csub\u3es\u3c/sub\u3e

Inclusive-jet cross sections have been measured in the reaction ep→e+jet+X for photon virtuality Q 2γp centre-of-mass energies in the region 142γp-1. Jets were identified using the k T, anti-k T or SIScone jet algorithms in the laboratory frame. Single-differential cross sections are presented as functions of the jet transverse energy, ETjet, and pseudorapidity, jet, for jets with ETjet\u3e17 GeV and -1\u3c je

Measurement of neutral current e+/-p cross sections at high Bjorken x with the ZEUS detector

The neutral current e+/-p cross section has been measured up to values of Bjorken x of approximately 1 with the ZEUS detector at HERA using an integrated luminosity of 187 inv. pb of e-p and 142 inv. pb of e+p collisions at sqrt(s) = 318GeV. Differential cross sections in x and Q2, the exchanged boson virtuality, are presented for Q2 geq 725GeV2. An improved reconstruction method and greatly increased amount of data allows a finer binning in the high-x region of the neutral current cross section and leads to a measurement with much improved precision compared to a similar earlier analysis. The measurements are compared to Standard Model expectations based on a variety of recent parton distribution functions.Comment: 39 pages, 9 figure

Measurement of the t Dependence in Exclusive Photoproduction of Υ{hooked} (1S) Mesons at HERA

The exclusive photoproduction reaction γp→Υ{hooked} (1S)p has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 468 pb -1. The measurement covers the kinematic range 6

Measurement of Beauty Production in Deep Inelastic Scattering at HERA Using Decays into Electrons

© The Author(s) 2011. The production of beauty quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared Q2 \u3e 10 GeV2, using an integrated luminosity of 363 pb-1. The beauty events were identified using electrons from semileptonic b decays with a transverse momentum 0.9 \u3c peT \u3c 8 GeV and pseudorapidity |ηe| \u3c 1.5. Cross sections for beauty production were measured and compared with next-to-leadingorder QCD calculations. The beauty contribution to the proton structure function F2 was extracted from the doubledifferential cross section as a function of Bjorken-x and Q2

Search for First-generation Leptoquarks at HERA

A search for first-generation leptoquarks was performed in electron-proton and positron-proton collisions recorded with the ZEUS detector at HERA in 2003-2007 using an integrated luminosity of 366pb-1. Final states with an electron and jets or with missing transverse momentum and jets were analyzed, searching for resonances or other deviations from the standard model predictions. No evidence for any leptoquark signal was found. The data were combined with data previously taken at HERA, resulting in a total integrated luminosity of 498pb-1. Limits on the Yukawa coupling, λ, of leptoquarks were set as a function of the leptoquark mass for different leptoquark types within the Buchmüller-Rückl-Wyler model. Leptoquarks with a coupling λ=0.3 are excluded for masses up to 699 GeV. © 2012 American Physical Society

Measurement of Inelastic J/ψ and ψ′ Photoproduction at HERA

The cross sections for inelastic photoproduction of J/ψ and ψ′ mesons have been measured in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb-1 collected in the period 1996-2007. The ψ′ to J/ψ cross section ratio was measured in the range 0.55 \u3c z \u3c 0.9 and 60 \u3c W \u3c 190 GeV as a function of W, z and pT. Here W denotes the photon-proton centre-of-mass energy, z is the fraction of the incident photon energy carried by the meson and p T is the transverse momentum of the meson with respect to the beam axis. The J/ψ cross sections were measured for 0.1 \u3c z \u3c 0.9, 60 \u3c W \u3c 240 GeV and pT \u3e 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 k T-factorisation approach. © 2013 SISSA

Search for Single-top Production in ep Collisions at HERA

A search for single-top production, ep→etX, has been performed with the ZEUS detector at HERA using data corresponding to an integrated luminosity of 0.37 fb -1. No evidence for top production was found, consistent with the expectation from the Standard Model. Limits were computed for single-top production via flavour changing neutral current transitions involving a neutral electroweak vector boson, γ or Z. The result was combined with a previous ZEUS result yielding a total luminosity of 0.50 fb -1. A 95% credibility level upper limit of 0.13 pb was obtained for the cross section at the centre-of-mass energy of √s=315 GeV. © 2012 Elsevier B.V

Measurement of Heavy-quark Jet Photoproduction at HERA

The Author(s) 2011. Photoproduction of beauty and charm quarks in events with at least two jets has been measured with the ZEUS detector at HERA using an integrated luminosity of 133 pb−1. The fractions of jets containing b and c quarks were extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of jet transverse momentum, pjetT, and pseudora pidity, ηjet, were measured. The data are compared with previous measurements and are well described by next-toleading- order QCD predictions

Scaled Momentum Distributions for K \u3csub\u3eS\u3c/sub\u3e\u3csup\u3e0\u3c/sup\u3e and ∧/∧ in DIS at HERA

Scaled momentum distributions for the strange hadrons K S0 and ∧/∧were measured in deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 330 pb -1. The evolution of these distributions with the photon virtuality, Q 2, was studied in the kinematic region 10 \u3c Q 2 \u3c 40000 GeV 2 and 0.001 \u3c x \u3c 0.75, where x is the Bjorken scaling variable. Clear scaling violations are observed. Predictions based on different approaches to fragmentation were compared to the measurements. Leading-logarithm parton-shower Monte Carlo calculations interfaced to the Lund string fragmentation model describe the data reasonably well in the whole range measured. Nextto-leading-order QCD calculations based on fragmentation functions, FFs, extracted from e +e - data alone, fail to describe the measurements. The calculations based on FFs extracted from a global analysis including e +e -, ep and pp data give an improved description. The measurements presented in this paper have the potential to further constrain the FFs of quarks, anti-quarks and gluons yielding K S0 and ∧/∧ strange hadrons. © SISSA 2012

Exclusive Electroproduction of Two Pions at HERA

The exclusive electroproduction of two pions in the mass range 0.