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  • 2000-2004  (8)
  • 1990-1994  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 11 (2001), S. 95-103 
    ISSN: 1434-601X
    Keywords: PACS. 13.60.-r Photon and charged-lepton interactions with hadrons – 13.60.Le Meson production – 25.20.-x Photonuclear reactions – 14.40.-n Mesons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Simulations based on a coupled-channel transport model have been performed to analyze the feasibility to study the in-medium ω mass exploiting the process γ + A→π0γ + X for C, Ca and Nb nuclei. The distortions due to final-state interactions of the π0 and background contributions from the reaction γ + A→π0π0 + X are found to be small in the mass range of interest ( 0.6 〈 M π0γ 〈 0.8 GeV). Furthermore, the effect of the detector resolution on the π0γ mass determination is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: PACS. 13.30.-a Decays of baryons – 13.75.Ev Hyperon-nucleon interaction – 21.80Hypernuclei – 25.80.Pw Hyperon-induced reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The lifetime of the Λ-hyperon for the nonmesonic decay ΛN → NN has been determined by a measurement at COSY Jülich of the delayed fission of heavy hypernuclei produced in proton-Au collisions at T p = 1.9 GeV. It is found that heavy hypernuclei with mass numbers A≈ (180±5) and atomic numbers Z≈ (74±2) fission with a lifetime τΛ = 130±13 (stat.) ±15 (syst.) ps. This value together with the results obtained for other heavy hypernuclei in previous investigations indicates --on the confidence level of 0.9-- a violation of the phenomenological ΔI = 1/2 rule for the ΛN → NN transitions as known from the weak mesonic decays of kaons and hyperons.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 7 (2000), S. 407-413 
    ISSN: 1434-601X
    Keywords: PACS: 12.10.Kt Unification of couplings – 12.40.Vv Vector-meson dominance – 13.75.Cs Nucleon-nucleon interactions – 13.75.Gx Pion-baryon interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The available data on ω and φ production from πN and pp collisions are reanalyzed with respect to an OZI rule violation on the basis of transition matrix elements. The data are found to be compatible with a constant ratio R , which however, deviates substantially from the SU(3) prediction based on the present knowledge of the φ-ω mixing angle.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 340 (1991), S. 287-295 
    ISSN: 1434-601X
    Keywords: 25.70.−z ; 25.70.Np
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Within a covariant BUU-approach we simulate heavyion collisions at various bombarding energies from 400 MeV/u to 1 GeV/u. We evaluate locally the energymomentum tensorT μv (x), and extract pressures, energydensities and temperatures. The connection of these thermodynamical quantities to experimental observables and their sensitivity to the equation of state is discussed. Furthermore, we investigate the question of local equilibration and evaluate the entropy produced in these reactions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 340 (1991), S. 51-57 
    ISSN: 1434-601X
    Keywords: 25.40.−h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The production ofη-mesons in proton-nucleus reactions is analysed with respect to primary nucleon-nucleon (NN→NNη) and secondary pion-nucleon (πN→ηN) production processes on the basis of Hartree-Fock groundstate momentum distributions and free on-shell production processes. The folding model adopted compares well for meson production with more involved simulations based on VUU transport equations. Similar to K+ production in proton-nucleus reactions theη-mesons are primarily produced by theπN →ηN channel. However,η-mesons are absorbed in nuclei via excitation of the N* (1535) resonance which leads to strong distortions of the primordial spectra. On the other hand, the experimental mass dependence of the differential cross sections might yield information about the in-medium properties of this resonance.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 348 (1994), S. 247-248 
    ISSN: 1434-601X
    Keywords: 25.40.-h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The production of antiprotons in proton-nucleus and deuteron-nucleus collisions is analyzed with respect to one-step nucleon-nucleon (NN → NNp¯ p) and secondary Δ-nucleon (ΔN → NNN¯ p) production channels within a phase-space model incorporating the selfenergies of the baryons. It is found that contrary to nucleus-nucleus collisions the Δ induced reaction channels are of minor importance except at very low bombarding energies. The data from KEK are approximately reproduced when accounting for the internal momentum distribution of the deuteron which provides a natural explanation for the large enhancement of the ¯p cross section ind+A as compared top+A.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-601X
    Keywords: 25.40.−h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The production ofK + mesons in proton-nucleus and deuteron-nucleus collisions is analyzed with respect to one-step nucleon-nucleon (NN → N ΛK +),Δ- nucleon (ΔN → N Λ K+) and two-step pion-nucleon (πN → K + Λ) production channels on the basis of experimental ground state momentum distributions and free on-shell production processes. Whereas forK + production in proton-nucleus reactions the secondary channelπN clearly dominates at subthreshold energies, meson and nucleon induced channels are of similar magnitude in deuteron-nucleus reactions. Contrary to nucleus-nucleus collisions theΔ induced reaction channels are found to be of minor importance. The experimental differentiation of the underlying microscopic reaction channels appears possible via differential proton —K + coincidence measurements as shown in detail by the microscopic simulations including proton rescattering.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 342 (1992), S. 161-167 
    ISSN: 1434-601X
    Keywords: 24.10.Cn ; 25.70.−z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a coupled set of equations for the one-body density matrix and the two-body correlation function consistent with trace relations and conservation laws which provide an extension of correlation dynamics on the two-body level. The additional interaction terms are discussed in the context of time-dependent G-matrix theory and NQCD and studied numerically by one-dimensional calculations for colliding finite fermion systems.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 339 (1991), S. 391-398 
    ISSN: 1434-601X
    Keywords: 14.80.Am ; 25.20.Gf ; 25.20.Lj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the differential cross section for nucleonnucleon bremsstrahlung in covariant way based on a realistic meson-exchange approximation for the NN-scattering amplitude. The results are discussed in comparison to semiclassical approximations and with respect to the role of internal radiation diagrams. The influence of the anomalous magnetic moment on the proton-neutron bremsstrahlung is found to contribute up to 50% for specific kinematical conditions. Recent measurements on the elementary differential cross sectionpn→pnγ are found to be quite accurately reproduced. Furthermore, for use in proton-nucleus and nucleus-nucleus collisions, we present a parametrization of thepnγ cross section within a broad kinematical range.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 337 (1990), S. 1-10 
    ISSN: 1434-601X
    Keywords: 05.60.+w ; 11.10.Qr ; 24.10.Cn ; 25.70.-z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present an extension of relativistic mean-field theories within the framework of quantum correlation dynamics starting from an effective hadronic Lagrangian density with minimal coupling between baryons and mesons. When neglecting retardation for the meson fields the conventional meson-exchange picture is obtained for the baryon-baryon interaction. The resulting equations of motion for the baryonic one-body density matrix and two-body correlation spinor matrix provide a nonperturbative framework for the description of relativistic heavy-ion collisions. Adopting semiclassical limits for the Wigner transform of the one-body density matrix a covariant transport equation is derived in the limit of time-dependent Dirac-Brueckner theory. It describes the mean-field dynamics including momentum-dependent potentials as well as in-medium nucleon-nucleon collisions on the basis of the same meson fields without double counting of interactions.
    Type of Medium: Electronic Resource
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