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Properties Of Hadronic Final States In Diffractive Deep Inelastic Ep Scattering At Desy Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

Characteristics of the hadronic final state of diffractive deep inelastic scattering events ep→eXp were studied in the kinematic range 4X35GeV, 4

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Searches For Excited Fermions In Ep Collisions At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

Searches in ep collisions for heavy excited fermions have been performed with the ZEUS detector at HERA. Excited states of electrons and quarks have been searched for in e+ p collisions at a centre-of-mass energy of 300 GeV using an integrated luminosity of 47.7 pb-1. Excited electrons have been sought via the decays e± → eγ, e± → eZ and e± → vW. Excited quarks have been sought via the decays q± → qγ and q± → qW. A search for excited neutrinos decaying via v± → vγ, v± → vZ and v± → eW is presented using e-p collisions …

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Inclusive Jet Cross Sections In The Breit Frame In Neutral Current Deep Inelastic Scattering At Hera And Determination Of Α S, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch, I. Brock

Faculty Publications

Inclusive jet differential cross sections have been measured in neutral current deep inelastic e +p scattering for boson virtualities Q 2 > 125 GeV 2. The data were taken using the ZEUS detector at HERA and correspond to an integrated luminosity of 38.6 pb -1. Jets were identified in the Breit frame using the longitudinally invariant k T cluster algorithm. Measurements of differential inclusive jet cross sections are presented as functions of jet transverse energy (E BT.jet), jet pseudorapidity and Q 2, for jets with E BT.jet > 8 GeV. Next-to-leading-order QCD calculations agree well with the measurements both at high Q …

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Measurement Of Diffractive Production Of D*±(2010) Mesons In Deep-Inelastic Scattering At Hera, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch, I. Brock

Faculty Publications

Diffractive production of D*±(2010) mesons in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 44.3 pb-1. Diffractive charm production is identified by the presence of a large rapidity gap in the final state of events in which a D*±(2010) meson is reconstructed in the decay channel D*+ → (D0 → K-π+)πs+ (+ charge conjugate). Differential cross sections when compared with theoretical predictions indicate the importance of gluons in such diffractive interactions. © 2002 Elsevier Science B.V. All rights reserved.

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Leading Neutron Production In E+ P Collisions At Hera, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan

Faculty Publications

The production of neutrons carrying at least 20% of the proton beam energy (xL > 0.2) in e+ p collisions has been studied with the ZEUS detector at HERA for a wide range of Q2, the photon virtuality, from photoproduction to deep inelastic scattering. The neutron-tagged cross section, ep → e′ Xn, is measured relative to the inclusive cross section, ep → e′ X, thereby reducing the systematic uncertainties. For xL > 0.3, the rate of neutrons in photoproduction is about half of that measured in hadroproduction, which constitutes a clear breaking of factorisation. There is about a 20% rise in the …

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Measurement Of High-Q 2 Charged Current Cross Sections In E - P Deep Inelastic Scattering At Hera, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch

Faculty Publications

Cross sections for e - p charged current deep inelastic scattering have been measured at a centre-of-mass energy of 318 GeV with an integrated luminosity of 16.4 pb -1 using the ZEUS detector at HERA. Differential cross sections dσ/dQ 2, dσ/dx and dσ/dy are presented for Q 2 > 200 GeV 2. In addition, d 2σ/(dxdQ 2) was measured in the kinematic range 280 GeV 2 < Q 2 < 30 000 GeV 2 and 0.015 < × < 0.42. The predictions of the Standard Model agree well with the measured cross sections. The mass of the W boson, determined from a fit to dσ/dQ 2, is M W = 80.3±2.1(stat.) ± 1.2(syst.) ± 1.0(PDF) GeV. © 2002 Published by Elsevier Science B.V.

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Exclusive Photoproduction Of J/Ψ Mesons At Hera, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi

Faculty Publications

The exclusive photoproduction of J/ψ mesons, γp → J/ψp, has been studied in ep collisions with the ZEUS detector at HERA, in the kinematic range 20 < W < 290 GeV, where W is the photon-proton centre-of-mass energy. The J/ψ mesons were reconstructed in the ninon and the electron decay channels using integrated luminosities of 38 pb-1 and 55 pb-1, respectively. The helicity structure of J/ψ production shows that the hypothesis of s-channel helicity conservation is satisfied within two standard deviations. The total cross section and the differential cross-section dσ/dt, where t is the squared four-momentum transfer at the proton vertex, are presented as a function of W, for |t| < 18 Ge2. The t distribution exhibits an exponential shape with a slope parameter increasing logarithmically with W with a value b = 4.15 ± 0.05(stat.)-0.18+0.30(syst.) GeV-2 at W = 90 GeV. The effective parameters of the Pomeron trajectory are αℙ(0) = 1.200 ± 0.009(stat.) -0.010+0.004(Syst.) and α′ℙ = 0.115 ± 0.018(stat.)-0.015+0.008(syst.) GeV-2.

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Search For Lepton-Flavor Violation In E+P Collisions At Desy Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

A search has been made for lepton-flavor-violating interactions of the type e+p→lX, where l denotes a μ or τ with high transverse momentum, at a center-of-mass energy √s of 300 GeV with an integrated luminosity of 47.7 pb-1 using the ZEUS detector at HERA. No evidence was found for lepton-flavor violation and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below √s, limits are set on λeq1βlq, where λeq1 is the coupling of the LQ to an electron and a first-generation quark q1 and βlq is the branching ration of the LQ to l …

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Measurement Of The Photon-Proton Total Cross Section At A Center-Of-Mass Energy Of 209 Gev At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

The photon-proton total cross section has been measured in the process e+ p → e+ γp → e+ X with the ZEUS detector at HERA. Events were collected with photon virtuality Q2 < 0.02 GeV2 and average γp center-of-mass energy Wγp = 209 GeV in a dedicated run, designed to control systematic effects, with an integrated luminosity of 49 nb-1. The measured total cross section is σtotγp = 174 ± 1 (stat.) ± 13 (syst.) μb. The energy dependence of the cross section is compatible with parameterizations of high-energy pp and pap data. © 2002 Elsevier Science B.V. All rights reserved.

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High-Mass Dijet Cross Sections In Photoproduction At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

Dijet differential cross sections for the reaction e+ p → e+ + jet + jet + X in the photoproduction regime have been measured with the ZEUS detector at HERA using an integrated luminosity of 42.7 pb-. The cross sections are given for photon-proton centre-of-mass energies in the range 134 < W < 277 GeV. The differential cross sections as a function of the dijet mass, MJJ, and of the dijet angular variables have been measured for 47 < MJJ < 160 GeV and compared to next-to-leading-order QCD calculations. The dijet events in the region 75 < MJJ < 100 GeV have been used to derive a 95% C.L. upper limit on the cross section for Z0 photoproduction of σ e+p→e+Z0X < 5.9 pb. Upper limits on the photoproduction of new heavy resonances decaying into two jets are also presented for masses in the range between 60 GeV and 155 GeV. © 2002 Elsevier Science B.V. All rights reserved.

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Dijet Photoproduction At Hera And The Structure Of The Photon, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

The dijet cross section in photoproduction has been measured with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb-1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1 GeV2 and a photon-proton centre-of-mass energy in the range 134 < Wγp < 277 GeV. Each event contains at least two jets satisfying transverse-energy requirements of ETjet1 > 14 GeV and ETjet2 > 11 GeV and pseudorapidity requirements of -1 < ηjet1,2 < 2.4. The measurements are compared to next-to-leading-order QCD predictions. The data show particular sensitivity to the density of partons in the photon, allowing the validity of the current parameterisations to be tested.

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Dijet Production In Neutral Current Deep Inelastic Scattering At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

Dijet cross sections in neutral current deep inelastic ep scattering have been measured in the range 10 < Q2 < 104 GeV 2 with the ZEUS detector at HERA using an integrated luminosity of 38.4 pb-1. The cross sections, measured in the Breit frame using the kT jet algorithm, are compared with next-to-leading-order perturbative QCD calculations using proton parton distribution functions. The uncertainties of the QCD calculations have been studied. The predictions are in reasonable agreement with the measured cross sections over the entire kinematic range.

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Measurement Of The Q2 And Energy Dependence Of Diffractive Dnteractions At Hera: The Zeus Collaboration, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Anzivino, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, C. Nemoz, F. Palmonari

Faculty Publications

Diffractive dissociation of virtual photons, γ*p → Xp, has been studied in ep interactions with the ZEUS detector at HERA. The data cover photon virtualities 0.17 < Q2 < 0.70 GeV2 and 3 < Q2 < 80 GeV2 with 3 < MX < 38 GeV, where MX is the mass of the hadronic final state. Diffractive events were selected by two methods: the first required the detection of the scattered proton in the ZEUS leading proton spectrometer (LPS); the second was based on the distribution of MX. The integrated luminosities of the low- and high-Q2 samples used in the LPS-based analysis are ≃ 0.9 pb-1 and ≃ 3.3 pb-1, respectively. The sample used for the MX-based analysis corresponds to an integrated luminosity of ≃ 6.2 pb-1. The dependence of the diffractive cross section on W, the virtual photon-proton centre-of-mass energy, and on Q2 is studied. In the low-Q2 range, the energy dependence is compatible with Regge theory and is used to determine the intercept of the Pomeron trajectory. The W dependence of the diffractive cross section exhibits no significant change from the low-Q2 to the high-Q2 region. In the low-Q2 range, little Q2 dependence is found, a significantly different behaviour from the rapidly falling cross section measured for Q2 > 3 GeV2. The ratio of the diffractive to the virtual photon-proton total cross section is studied as a function of W and Q2. Comparisons are made with a model based on perturbative QCD.

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