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  • 2000-2004  (172)
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  • 1
    Digitale Medien
    Digitale Medien
    QCD analyses and determinations of $\alpha_s$ in ${\rm e}^+{\rm e}^-$ annihilation at energies between 35 and 189 GeV (2000)
    Springer
    The European physical journal 17 (2000), S. 19-51 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. We employ data taken by the JADE and OPAL experiments for an integrated QCD study in hadronic e $^+$ e $^-$ annihilations at c.m.s. energies ranging from 35 GeV through 189 GeV. The study is based on jet-multiplicity related observables. The observables are obtained to high jet resolution scales with the JADE, Durham, Cambridge and cone jet finders, and compared with the predictions of various QCD and Monte Carlo models. The strong coupling strength, $\alpha_s$ , is determined at each energy by fits of ${\cal O}(\alpha_s^2)$ calculations, as well as matched ${\cal O}(\alpha_s^2)$ and NLLA predictions, to the data. Matching schemes are compared, and the dependence of the results on the choice of the renormalization scale is investigated. The combination of the results using matched predictions gives \[\alpha_s(M_{Z^0})=0.1187^{0.0034}_{0.0019}.\] The strong coupling is also obtained, at lower precision, from ${\cal O}(\alpha_s^2)$ fits of the c.m.s. energy evolution of some of the observables. A qualitative comparison is made between the data and a recent MLLA prediction for mean jet multiplicities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100520000432
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  • 2
    facet.materialart.
    Unbekannt
    Towards automation of computing fabrics using tools from the fabric management workpackage of the EU DataGrid project (2003)
    Details
    Publikationsdatum: 2021-01-21
    Sprache: Englisch
    Materialart: conferenceobject , doc-type:conferenceObject
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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    OPUS
  • 3
    Digitale Medien
    Digitale Medien
    Letters to the Editor (2003)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 54 (2003), S. 0 
    Details
    ISSN: 1365-2389
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2389.2003.00534.x
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  • 4
    Digitale Medien
    Digitale Medien
    Search for resonant $\tilde\nu$ production at $\sqrt{s} = $ 183 to 208 GeV (2003)
    Springer
    The European physical journal 28 (2003), S. 15-26 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. Searches for resonant $\tilde\nu$ production in e + e - collisions under the assumption that R-parity is not conserved and that the dominant R-parity violating coupling is $\lambda_{121}$ or $\lambda_{131}$ used data recorded by DELPHI in 1997 to 2000 at centre-of-mass energies of 183 to 208 GeV. No deviation from the Standard Model was observed. Upper limits are given for the $\lambda_{121}$ and $\lambda_{131}$ couplings as a function of the sneutrino mass and total width. The limits are especially stringent for sneutrino masses equal to the centre-of-mass energies with the highest integrated luminosities recorded.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1140/epjc/s2003-01158-8
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  • 5
    Digitale Medien
    Digitale Medien
    Single- and multi-photon production in ee collisions at $\sqrt{s}$ up to 209 GeV (2003)
    Springer
    The European physical journal 28 (2003), S. 1-13 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. Events containing only energetic photons are analysed in a sample of $628 \mathrm{pb}^{-1}$ of data recorded from $\rm e^+e^-$ collisions at centre-of-mass energies between 189 and 209 GeV by the ALEPH detector at LEP. The $e^+ e^-\to \nu\bar{\nu}\gamma(\gamma)$ and $e^+ e^-\to \gamma\gamma(\gamma)$ cross sections are measured and found to be in agreement with the standard model predictions. The number of light neutrino generations is determined to be $N_\nu = 2.86 \pm 0.09$ . Upper limits are derived on the cross sections for photon production in the context of several supersymmetric models. Limits are also set on the parameters of models with extra spatial dimensions, with contact interactions and with excited electrons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1140/epjc/s2002-01129-7
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    A measurement of the photonuclear interactions of 180 GeV muons in iron (2003)
    Springer
    The European physical journal 28 (2003), S. 297-304 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. The energy spectrum and the cross section of photonuclear interactions of 180 GeV muons in iron were measured at the CERN SPS using prototype modules of the ATLAS hadron calorimeter. The differential cross section $(N_{A}/A)v{d}\sigma/{d}v$ for a muon fractional energy loss $v = \Delta E_{\mu} / E_{\mu}$ was measured in the range 0.1〈v〈1. The integrated cross section $(N_{A}/A) \int_{0.1}^{1} v{d}\s igma/{d}v$ is $(0.26 \pm 0.03_{stat} \pm 0.03_{syst})\cdot 10^{-6}$ cm2g-1 in agreement with the theoretical prediction of $0.267 \cdot 10^{-6}$ cm2g-1. The best adjustment of the data to the theory is achieved for the value of $\sigma_{\gamma N} = (115 \pm 18_stat \pm 15_{syst})\mu {b}$ of the photon-nucleon cross section for photons with energies in the range from 18 to 180 GeV.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1140/epjc/s2003-01176-6
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  • 7
    Digitale Medien
    Digitale Medien
    Measurement of the inclusive D $^{*\pm}$ production in $\gamma\gamma$ collisions at LEP (2003)
    Springer
    The European physical journal 28 (2003), S. 437-449 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. The inclusive production of D $^{*\pm}$ mesons in two-photon collisions is measured with the ALEPH detector at e+e- centre-of-mass energies from 183 GeV to 209 GeV. A total of $360 \pm 27$ D $^{*\pm}$ meson events are observed from an integrated luminosity of 699pb-1. Contributions from direct and single-resolved processes are separated using the ratio of the transverse momentum $p_{t}^{D^{*\pm}}$ of the D $^{*\pm}$ to the visible invariant mass Wvis of the event. Differential cross sections of D $^{*\pm}$ production as functions of $p_{t}^{D^{*\pm}}$ and the pseudorapidity $\vert\eta^{D^{*\pm}}\vert $ are measured in the range 2 GeV $/c 〈 p_{t}^{D^{*\pm}} 〈 12$ GeV/c and $ \vert\eta^{D^{*\pm}}\vert 〈 1.5 $ . They are compared to next-to-leading order (NLO) perturbative QCD calculations. The extrapolation of the integrated visible D $^{*\pm}$ cross section to the total charm cross section, based on the Pythia Monte Carlo program, yields $ \sigma (e^+e^- \rightarrow e^+e^- c\bar{c})_{\left〈\sqrt{s}\right〉 = 197 GeV} = 731 \pm 74_{stat} \pm 47_{syst} \pm 157_{extr}$ pb .
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1140/epjc/s2003-01201-x
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  • 8
    Digitale Medien
    Digitale Medien
    Search for R-parity violating decays of scalar fermions at LEP (2000)
    Springer
    The European physical journal 12 (2000), S. 1-24 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. A search for pair produced scalar fermions with couplings that violate R-parity has been performed using a data sample corresponding to an integrated luminosity of 56 pb $^{-1}$ at a centre-of-mass energy of $\sqrt{s}=$ 183 GeV collected with the OPAL detector at LEP. An important consequence of R-parity breaking interactions is that the lightest supersymmetric particle is expected to be unstable. Searches for R-parity violating decays of charged sleptons, sneutrinos and stop quarks have been performed under the assumptions that the lightest supersymmetric particle decays promptly and that only one of the R-parity violating couplings is dominant for each of the decay modes considered. Such processes would yield multi-leptons, jets plus leptons or multi-jets, with or without missing energy, in the final state. No significant excess of such events has been observed. Limits on the production cross-sections of scalar fermions in R-parity violating scenarios are obtained. Mass exclusion regions are also presented in the framework of the Constrained Minimal Supersymmetric Standard Model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100529900226
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  • 9
    Digitale Medien
    Digitale Medien
    Measurement of $D^{\ast \pm}$ production and the charm contribution to $F_2$ in deep inelastic scattering at HERA (2000)
    Springer
    The European physical journal 12 (2000), S. 35-52 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. The production of $D^{\ast \pm}$ (2010) mesons in deep inelastic scattering has been measured in the ZEUS detector at HERA using an integrated luminosity of 37 pb $^{-1}$ . The decay channels $D^{\ast +}\rightarrow D^0 \pi^+ $ (+ c.c.), with $D^0 \rightarrow K^- \pi^+$ or $D^0 \rightarrow K^- \pi^- \pi^+ \pi^+$ , have been used to identify the D mesons. The $e^+p$ cross section for inclusive $D^{\ast \pm}$ production with $1 〈 Q^2 〈 600\,$ GeV $^2$ and $0.02〈 y 〈 0.7$ is $8.31 \pm 0.31 \mbox{(stat.)}^{+0.30}_{-0.50}\mbox{(syst.)}$ nb in the kinematic region $1.5 〈 p_T(D^{\ast \pm}) 〈 15$ GeV and $|\eta(D^{\ast \pm})| 〈 1.5$ . Differential cross sections are consistent with a next-to-leading-order perturbative-QCD calculation when using charm-fragmentation models which take into account the interaction of the charm quark with the proton remnant. The observed cross section is extrapolated to the full kinematic region in $p_T(D^{\ast \pm})$ and $\eta(D^{\ast \pm})$ in order to determine the charm contribution, $F_{2}^{c\bar c}(x,Q^2)$ , to the proton structure function. The ratio $F_{2}^{c\bar c}/F_{2}$ rises from $\simeq$ 10% at $Q^2 \simeq$ 1.8 GeV $^2$ to $\simeq$ 30% at $Q^2 \simeq $ 130 GeV $^2$ for x values in the range $10^{-4}$ to $10^{-3}$ .
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100529900244
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  • 10
    Digitale Medien
    Digitale Medien
    Measurement of the spin-density matrix elements in exclusive electroproduction of $\rho^0$ mesons at HERA (2000)
    Springer
    The European physical journal 12 (2000), S. 393-410 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. Exclusive electroproduction of $\rho^0$ mesons has been measured using the ZEUS detector at HERA in two $Q^2$ ranges, $0.25 〈 Q^2 〈 0.85$ GeV $^2$ and $3〈 Q^2 〈 30$ GeV $^2$ . The low- $Q^2$ data span the range $20 〈 W 〈 90$ GeV; the high- $Q^2$ data cover the $40 〈 W 〈 120$ GeV interval. Both samples extend up to four-momentum transfers of $|t|=0.6$ GeV $^2$ . The distribution in the azimuthal angle between the positron scattering plane and the $\rho^0$ production plane shows a small but significant violation of s-channel helicity conservation, corresponding to the production of longitudinally polarised (i.e. helicity zero) $\rho^0$ mesons from transverse photons. Measurements of the 15 combinations of spin-density matrix elements which completely define the angular distributions are presented and discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100529900246
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