| 1. |
- Aktas, A., et al.
(författare)
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Inclusive D*(+/-) meson and associated dijet production in deep-inelastic scattering at HERA
- 2007
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 51:2, s. 271-287
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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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| 2. |
- Aktas, A., et al.
(författare)
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Inclusive D-*+/- meson cross sections and D-*+/--jet correlations in photoproduction at HERA
- 2007
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 50:2, s. 251-267
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Tidskriftsartikel (refereegranskat)abstract
- Differential photoproduction cross sections are measured for events containing D-*+/- mesons. The data were taken with the H1 detector at the ep collider HERA and correspond to an integrated luminosity of 51.1 pb(-1). The kinematic region covers small photon virtualities Q(2) < 0.01 GeV2 and photon-proton centre-of-mass energies of 171 < W gamma(Cep) < 256 GeV. The details of the heavy quark production process are further investigated in events with one or two jets in addition to the D-*+/- meson. Differential cross sections for D-* + jet production are determined and the correlations between the D-*+/- meson and the jet(s) are studied. The results are compared with perturbative QCD predictions applying collinear- or k(t)-factorisation.
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| 3. |
- Aktas, A., et al.
(författare)
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Measurement of inclusive jet production in deep-inelastic scattering at high Q(2) and determination of the strong coupling
- 2007
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 653:2-4, s. 134-144
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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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| 4. |
- Aktas, A., et al.
(författare)
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Tests of QCD factorisation in the diffractive production of dijets in deep-inelastic scattering and photoproduction at HERA
- 2007
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 51:3, s. 549-568
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Tidskriftsartikel (refereegranskat)abstract
- Measurements are presented of differential dijet cross sections in diffractive photoproduction (Q(2) < 0.01 GeV2) and deep-inelastic scattering processes (DIS, 4 < Q2 < 80 GeV2). The event topology is given by ep -> eXY, in which the system X, containing at least two jets, is separated from a leading low-mass baryonic system Y by a large rapidity gap. The dijet cross sections are compared with NLO QCD predictions based on diffractive parton densities previously obtained from a QCD analysis of inclusive diffractive DIS cross sections by H1. In DIS, the dijet data are well described, supporting the validity of QCD factorisation. The diffractive DIS dijet data are more sensitive to the diffractive gluon density at high fractional parton momentum than the measurements of inclusive diffractive DIS. In photoproduction, the predicted dijet cross section has to be multiplied by a factor of approximately 0.5 for both direct and resolved photon interactions to describe the measurements. The ratio of measured dijet cross section to NLO prediction in photoproduction is a factor 0.5 +/- 0.1 smaller than the same ratio in DIS. This suppression is the first clear observation of QCD hard scattering factorisation breaking at HERA. The measurements are also compared to the two soft colour neutralisation models SCI and GAL. The SCI model describes diffractive dijet production in DIS but not in photoproduction. The GAL model fails in both kinematic regions.
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