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Träfflista för sökning "WFRF:(Smiljanic R.) ;pers:(Chekelian V.)"

Sökning: WFRF:(Smiljanic R.) > Chekelian V.

  • Resultat 1-10 av 41
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1.
  • Aaron, F. D., et al. (författare)
  • Multi-leptons with high transverse momentum at HERA
  • 2009
  • Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; :10
  • Tidskriftsartikel (refereegranskat)abstract
    • Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb(-1). The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e(+)p collision data with a scalar sum of the lepton transverse momenta above 100 GeV while 1.94 +/- 0.17 events are expected. Such events are not observed in e(-)p collisions for which 1.19 +/- 0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions.
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2.
  • Aaron, F. D., et al. (författare)
  • Combined measurement and QCD analysis of the inclusive e(+/-)p scattering cross sections at HERA
  • 2010
  • Ingår i: Journal of High Energy Physics. - 1029-8479. ; :1
  • Tidskriftsartikel (refereegranskat)abstract
    • A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral and charged current unpolarised e(+/-)p scattering at HERA during the period 1994-2000. The data span six orders of magnitude in negative four-momentum-transfer squared, Q(2), and in Bjorken x. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy. The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions, HERAPDF1.0, with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the fit result.
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3.
  • Aaron, F. D., et al. (författare)
  • Events with an isolated lepton and missing transverse momentum and measurement of W production at HERA
  • 2010
  • Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2010:3, s. 1-19
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for events containing an isolated electron or muon and missing trans verse momentum produced in e(+/-)p collisions is performed with the H1 and ZEUS detectors at HERA. The data were taken in the period 1994-2007 and correspond to an integrated luminosity of 0.98 fb(-1). The observed event yields are in good overall agreement with the Standard Model prediction, which is dominated by single W production. In the e(+)p data, at large hadronic transverse momentum P-T(X) > 25GeV, a total of 23 events are observed compared to a prediction of 14.0 +/- 1.9. The total single W boson production cross section is measured as 1.06 +/- 0.16 (stat.) +/- 0.07 (sys.) pb, in agreement with an Standard Model (SM) expectation of 1.26 +/- 0.19 pb.
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4.
  • Aaron, F. D., et al. (författare)
  • Search for first generation leptoquarks in ep collisions at HERA
  • 2011
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 704:5, s. 388-396
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for first generation scalar and vector leptoquarks produced in ep collisions is performed by the H1 experiment at HERA. The full H1 data sample is used in the analysis, corresponding to an integrated luminosity of 446 pb(-1). No evidence for the production of leptoquarks is observed in final states with a large transverse momentum electron or with large missing transverse momentum, and constraints on leptoquark models are derived. For leptoquark couplings of electromagnetic strength lambda = 0.3, first generation leptoquarks with masses up to 800 GeV are excluded at 95% confidence level. (C) 2011 Elsevier B.V. All rights reserved.
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5.
  • Aaron, F. D., et al. (författare)
  • Measurement of isolated photon production in deep-inelastic scattering at HERA
  • 2008
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 54:3, s. 371-387
  • Tidskriftsartikel (refereegranskat)abstract
    • The production of isolated photons in deep-inelastic scattering ep -> e gamma X is measured with the H1 detector at HERA. The measurement is performed in the kinematic range of negative four-momentum transfer squared 4 < Q(2)< 150 GeV2 and a mass of the hadronic system W-X > 50 GeV. The analysis is based on a total integrated luminosity of 227 pb(-1). The production cross section of isolated photons with a transverse energy in the range 3 < E-T(gamma)< 10 GeV and pseudorapidity range -1.2
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6.
  • Aaron, F. D., et al. (författare)
  • Observation of the hadronic final state charge asymmetry in high Q(2) deep-inelastic scattering at HERA
  • 2009
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 681:2, s. 125-133
  • Tidskriftsartikel (refereegranskat)abstract
    • A first measurement is presented of the charge asymmetry in the hadronic final state from the hard interaction in deep-inelastic ep neutral current scattering at HERA. The measurement is performed in the range of negative squared four momentum transfer 100 < Q(2) < 8000 GeV2. The difference between the event normalised distributions of the scaled momentum, x(p), for positively and negatively charged particles, measured in the current region of the Breit frame, is studied together with its evolution as a function of Q. The results are compared to Monte Carlo models at the hadron and parton levels. (C) 2009 Elsevier B.V. All rights reserved.
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7.
  • Aaron, F. D., et al. (författare)
  • Three- and four-jet production at low x at HERA
  • 2008
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 54:3, s. 389-409
  • Tidskriftsartikel (refereegranskat)abstract
    • Three- and four-jet production is measured in deep-inelastic ep scattering at low x and Q(2) with the H1 detector using an integrated luminosity of 44.2 pb(-1). Several phase space regions are selected for the three-jet analysis in order to study the underlying parton dynamics from global topologies to the more restrictive regions of forward jets close to the proton direction. The measurements of cross sections for events with at least three jets are compared to fixed order QCD predictions of O(alpha(2)(s)) and O(alpha(3)(s)) and with Monte Carlo simulation programs where higher order effects are approximated by parton showers. A good overall description is provided by the O(alpha(3)(s)) calculation. Too few events are predicted at the lowest x similar to 10(-4), especially for topologies with two forward jets. This hints to large contributions at low x from initial state radiation of gluons close to the proton direction and unordered in transverse momentum. The Monte Carlo program in which gluon radiation is generated by the colour dipole model gives a good description of both the three- and the four-jet data in absolute normalisation and shape.
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8.
  • Aktas, A., et al. (författare)
  • Measurement of inclusive jet production in deep-inelastic scattering at high Q(2) and determination of the strong coupling
  • 2007
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 653:2-4, s. 134-144
  • Tidskriftsartikel (refereegranskat)abstract
    • Inclusive jet production is studied in neutral current deep-inelastic positron-proton scattering at large four momentum transfer squared Q(2) > 150 GeV2 with the H1 detector at HERA. Single and double differential inclusive jet cross sections are measured as a function of Q(2) and of the transverse energy E-T of the jets in the Breit frame. The measurements are found to be well described by calculations at next-to-leading order in perturbative QCD. The running of the strong coupling is demonstrated and the value of alpha(s)(M-Z) is determined. The ratio of the inclusive jet cross section to the inclusive neutral current cross section is also measured and used to extract a precise value for ces (M-Z) = 0.1193 +/- 0.0014(exp.)(-0.0030)(+0.0047) (th.) +/- 0.0016(pdf). (c) 2007 Elsevier BX All rights reserved.
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9.
  • Aaron, F. D., et al. (författare)
  • A precision measurement of the inclusive ep scattering cross section at HERA
  • 2009
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 64:4, s. 561-587
  • Tidskriftsartikel (refereegranskat)abstract
    • A measurement of the inclusive deep inelastic neutral current e(+) p scattering cross section is reported in the region of four-momentum transfer squared, 12GeV(2) <= Q(2) <= 150 GeV2, and Bjorken x, 2 x 10(-4) <= x <= 0.1. The results are based on data collected by the H1 Collaboration at the ep collider HERA at positron and proton beam energies of E-e = 27.6 GeV and E-p = 920 GeV, respectively. The data are combined with previously published data, taken at E-p = 820 GeV. The accuracy of the combined measurement is typically in the range of 1.3-2%. A QCD analysis at next-to-leading order is performed to determine the parton distributions in the proton based on H1 data.
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10.
  • Aktas, A., et al. (författare)
  • Inclusive D*(+/-) meson and associated dijet production in deep-inelastic scattering at HERA
  • 2007
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 51:2, s. 271-287
  • Tidskriftsartikel (refereegranskat)abstract
    • Inclusive D*(+/-) production is measured in deep-inelastic ep scattering at HERA with the H1 detector. In addition, the production of dijets in events with a D*(+/-) meson is investigated. The analysis covers values of photon virtuality 2 <= Q(2) <= 100 GeV2 and of inelasticity 0.05 <= y <= 0.7. Differential cross sections are measured as a function of Q(2) and x and of various D*(+/-) meson and jet observables. Within the experimental and theoretical uncertainties all measured cross sections are found to be adequately described by next-to-leading order (NLO) QCD calculations, based on the photon - gluon fusion process and DGLAP evolution, without the need for an additional resolved component of the photon beyond what is included at NLO. A reasonable description of the data is also achieved by a prediction based on the CCFM evolution of partons involving the kT- unintegrated gluon distribution of the proton.
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  • Resultat 1-10 av 41

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