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Sökning: WFRF:(Muller H) > Schoeffel L.

  • Resultat 1-10 av 46
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1.
  • Aad, G., et al. (författare)
  • 2013
  • Tidskriftsartikel (refereegranskat)
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2.
  • Aad, G., et al. (författare)
  • 2013
  • Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :4
  • Tidskriftsartikel (refereegranskat)
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3.
  • Aaron, F. D., et al. (författare)
  • Measurement of charm and beauty jets in deep inelastic scattering at HERA
  • 2011
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Measurements of cross sections for events with charm and beauty jets in deep inelastic scattering at HERA are presented. Events with jets of transverse energy E-T(jet) > 6 GeV and pseudorapidity - 1.0 < eta(jet) < 1.5 in the laboratory frame are selected in the kinematic region of photon virtuality Q(2) > 6 GeV2 and inelasticity variable 0.07 < y < 0.625. Measurements are also made requiring a jet in the Breit frame with E-T(*jet) > 6 GeV. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb(-1). The numbers of charm and beauty jets are determined using variables reconstructed using the H1 vertex detector with which the impact parameters of the tracks to the primary vertex and the position of secondary vertices are measured. The measurements are compared with QCD predictions and with previous measurements where heavy flavours are identified using muons.
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4.
  • Aaron, F. D., et al. (författare)
  • Inelastic production of J/psi mesons in photoproduction and deep inelastic scattering at HERA
  • 2010
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 68:3-4, s. 401-420
  • Tidskriftsartikel (refereegranskat)abstract
    • A measurement is presented of inelastic photoand electroproduction of J/psi mesons in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and the helicity distributions of the J/psi mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non- relativistic QCD. Calculations in the colour singlet model using a k(T) factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next- to- leading order in collinear factorisation underestimate the data.
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5.
  • Aktas, A, et al. (författare)
  • A direct search for stable magnetic monopoles produced in positron-proton collisions at HERA
  • 2005
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 41, s. 133-141
  • Tidskriftsartikel (refereegranskat)abstract
    • A direct search has been made for magnetic monopoles produced in e(+)p collisions at a centre of mass energy of 300 GeV at HERA. The beam pipe surrounding the interaction region in 1995-1997 was investigated using a SQUID magnetometer to look for stopped magnetic monopoles. During this time an integrated luminosity of 62 pb(-1) was delivered. No magnetic monopoles were observed and charge and mass dependent upper limits on the e(+)p production cross section are set.
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6.
  • Adloff, C, et al. (författare)
  • Energy flow and rapidity gaps between jets in photoproduction at HERA
  • 2002
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 24:4, s. 517-527
  • Tidskriftsartikel (refereegranskat)abstract
    • Dijet events in photon-proton collisions in which there is a large pseudorapidity separation, Deltaeta > 2.5 between the two highest E-T jets are studied with the H1 detector at HERA. The inclusive dijet cross sections are measured as functions of the longitudinal momentum fractions of the proton and photon which participate in the production of the jets, x(p)(jets) and x(gamma)(jets) respectively, Deltaeta, the pseudorapidity P separation between the two highest E-T jets, and E-T(gap), the total summed transverse energy between the jets. Rapidity gap events are defined as events in which E-T(gap) is less than E-T(cut), for E-T(cut) varied between jets 0.5 and 2.0 GeV. The fraction of dijet events with a rapidity gap is measured differentially in Deltaeta, x(p)(jets) and x(gamma)(jets). An excess of events with rapidity gaps at low values of E-T(cut) is observed above the expectation from standard photoproduction processes. This excess can be explained by the exchange of a strongly interacting colour singlet object between the jets.
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7.
  • Adloff, C, et al. (författare)
  • Measurement of dijet cross sections in photoproduction at HERA
  • 2002
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 13-23
  • Tidskriftsartikel (refereegranskat)abstract
    • Dijet cross sections as functions of several jet observables are measured in photoproduction using the HI detector at HERA. The data sample comprises e(+)p data with an integrated luminosity of 319 pb(-1). Jets are selected using the inclusive k(perpendicular to) algorithm with a minimum transverse energy of 25 GeV for the leading jet. The phase space covers longitudinal proton momentum fraction x(p) and photon longitudinal momentum fraction x(gamma) in the ranges 0.05 < x(p) < 0.6 and 0.1 < x(gamma) < 1. The predict ions of next-to-leading order perturbative QCD, including recent photon and proton parton densities, are found to be compatible with the data in a wide kinematical range.
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8.
  • Aktas, A, et al. (författare)
  • Muon pair production in ep collisions at HERA
  • 2004
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 583:1-2, s. 28-40
  • Tidskriftsartikel (refereegranskat)abstract
    • Cross sections for the production of two isolated muons up to high di-muon masses are measured in ep collisions at HERA with the H1 detector in a data sample corresponding to an integrated luminosity of 71 pb(-1) at a centre of mass energy of roots = 319 GeV. The results are in good agreement with Standard Model predictions, the dominant process being photon-photon interactions. Additional muons or electrons are searched for in events with two high transverse momentum muons using the full data sample corresponding to 114 pb(-1), where data at roots = 301 GeV and roots = 319 GeV are combined. Both the di-lepton sample and the tri-lepton sample agree Well with the predictions. (C) 2004 Published by Elsevier B.V.
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9.
  • Adloff, C, et al. (författare)
  • A measurement of the t dependence of the helicity structure of diffractive rho meson electroproduction at HERA
  • 2002
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 539:1-2, s. 25-39
  • Tidskriftsartikel (refereegranskat)abstract
    • The helicity structure of the diffractive electroproduction of rho mesons, e + p --> e + rho + Y, is studied in a previously unexplored region of large four-momentum transfer squared at the proton vertex, t: 0 < t' < 3 GeV2, where t' = - min. The data used are collected with the HI detector at HERA in the kinematic domain 2.5 < Q(2) < 60 GeV2, 40 < W < 120 GeV No t dependence of the r(00)(04) spin density matrix element is found. A significant t dependent helicity non-conservation from the virtual photon to the rho meson is observed for the spin density matrix element combinations r(00)(5) + 2r(11)(5) and r(00)(1) + 2r(11)(1). These t dependences are consistently described by a perturbative QCD model based on the exchange of two gluons.
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10.
  • Adloff, C, et al. (författare)
  • Measurement of D*(+/-) meson production and F-2(c) in deep-inelastic scattering at HERA
  • 2002
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 528:3-4, s. 199-214
  • Tidskriftsartikel (refereegranskat)abstract
    • The inclusive production of D*+/-(2010) mesons in deep-inelastic scattering is studied with the HI detector at HERA. In the kinematic region 1 < Q(2) < 100 GeV2 and 0.05 < y < 0.7 an e(+) p cross section for inclusive D*+/- meson production of 8.50 +/- 0.42(stat.)(-100)(+1.21)(syst.) nb is measured in the visible range p(tD*) > 1.5 GeV and eta(D*) < 1.5. Single and double differential inclusive D*+/- meson cross sections are compared to perturbative QCD calculations in two different evolution schemes, The charm contribution to the proton structure, F-c(2)(x, Q(2)), is determined by extrapolating the visible charm cross section to the full phase space. This contribution is found to rise from about 10% at Q(2) = 1.5 GeV2 to more than 25% at Q(2) = 60 GeV2 corresponding to x values ranging from 5 x 10(-5) to 3 x 10(-3). (C) 2002 Elsevier Science B.V. All rights reserved.
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