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  • 2000-2004  (8)
  • 1985-1989  (9)
  • 1
    Digitale Medien
    Digitale Medien
    Studying the ω mass in-medium in γ + A →π0γ + X reactions (2001)
    Springer
    The European physical journal 11 (2001), S. 95-103 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 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
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100500170099
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  • 2
    Digitale Medien
    Digitale Medien
    Nonmesonic decay of the Λ-hyperon in hypernuclei produced by p + Au collisions (2001)
    Springer
    The European physical journal 11 (2001), S. 1-4 
    Details
    ISSN: 1434-601X
    Schlagwort(e): PACS. 13.30.-a Decays of baryons – 13.75.Ev Hyperon-nucleon interaction – 21.80Hypernuclei – 25.80.Pw Hyperon-induced reactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100500170089
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  • 3
    Digitale Medien
    Digitale Medien
    On the current status of OZI violation in πN and pp reactions (2000)
    Springer
    The European physical journal 7 (2000), S. 407-413 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 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
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00013625
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  • 4
    Digitale Medien
    Digitale Medien
    A quantal toy model for heavy-ion collisions (1987)
    Springer
    The European physical journal 326 (1987), S. 21-31 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70.−z ; 25.70.Lm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A one-dimensional toy model of two moving finite boxes is analysed with respect to quantal phenomena associated with heavy-ion dynamics at low and intermediate energies. Special attention is payed to the relation between energy and momentum of the nucleons inside and outside the time-dependent mean field. A Wigner transformation of the one-body density matrix in space and time allows for a unique comparison with classical phase-space dynamics. It is found that high momentum components of the nuclear groundstate wave function approximately become on-shell during the heavy-ion reaction. This leads to the emission of energetic nucleons which do not appear classically. It is furthermore shown, that the low lying eigenstates of the dinuclear system for fixed time are only partly occupied throughout the reaction at intermediate energies. This opens up final phase space for nucleons after producing e.g. a pion or energetic photon. Though the present model does not allow for a reliable calculation of double differential nucleon spectra, pion or photon cross sections, it transparently shows the peculiar features of quantum dynamics in heavy-ion collisions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294567
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  • 5
    Digitale Medien
    Digitale Medien
    Microscopic investigations of pion production in heavy-ion collisions (1987)
    Springer
    The European physical journal 326 (1987), S. 97-106 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70−z ; 25.90+k ; 13.75 Gx
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Production mechanisms for subthreshold pions in nucleus-nucleus collisions are studied on a microscopic level. The non-relativistic expansion of the pseudoscalar πNN-vertex provides a basis for the construction of several two-nucleon models. These are incorporated into a dynamical description of the heavy-ion collision by boosted harmonic oscillators that adopts essential features from TDHF. The approach allows for a separate analysis of the various production processes and the influence of the collision dynamics on the total pion yield. Results are presented for the system16O +16O at laboratory energies of 40 and 80 MeV per nucleon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294576
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  • 6
    Digitale Medien
    Digitale Medien
    Numerical study of a selfconsistent two-body theory for colliding ions in a one-dimensional model (1987)
    Springer
    The European physical journal 328 (1987), S. 423-429 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 24.10.Cn ; 24.10.−i
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A selfconsistent quantal two-body theory as obtained from the density-matrix hierarchy is solved numerically for the first time for a one-dimensional system modelling α+ α collisions at 80 MeV/u. Various truncation schemes for the two-body correlation function are investigated in order to explore the convergence properties of the theory. We find that perturbative treatments with respect to two-body processes do not yield reliable results in the energy regime investigated and that the nuclear stopping power sensitively depends on the order of the two-body correlations considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01289628
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  • 7
    Digitale Medien
    Digitale Medien
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1988)
    Springer
    The European physical journal 329 (1988), S. 487-495 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 24.10.-i ; 25.70.-z ; 25.80.Ls
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The production of pions in intermediate energy nucleus-nucleus collisions by incoherent nucleon-nucleon collisions is studied within a microscopic quantal phase-space approach. Employing free production rates for the elementary processN+N → π+X experimental data for inclusive pion yields are approximately reproduced from 20–150 MeV/u within the first collision approximation. These results indicate that cooperative phenomena — apart from the time-dependent mean field — seem to play a minor role for energetic particle production even at very low bombarding energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294353
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  • 8
    Digitale Medien
    Digitale Medien
    Quark deconfinement in a semiclassical string-bag model (1987)
    Springer
    The European physical journal 327 (1987), S. 243-249 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 11.15Kc ; 12.35Ht ; 12.40Qq
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We describe the effective static quark-(anti)quark colour potential inside hadronic bags in terms of linear strings and semiclassical corrections of orderħ/r. According to (chromo-) electrostatics we generalize this potential to colour non-neutral configurations making use of the mirror charge method. A thermodynamical study of quark-antiquark pairs and many-quark systems shows a virtually higher order phase transition from the hadronic phase to colour deconfinement. The free plasma stage, furthermore, is achieved only at temperatures much higher thanT c≈200 MeV. Hadrons increase in size by a factor of 1.5 fromT=0 toT=T c.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01284447
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  • 9
    Digitale Medien
    Digitale Medien
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1987)
    Springer
    The European physical journal 327 (1987), S. 447-460 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70.-z ; 25.70.Lm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The Uehling-Uhlenbeck collision term is derived from coupled equations of motion for the one-body density matrix and the two-body correlation function as obtained from the density-matrix hierarchy. The respective approximations introduced are related with energy and momentum conservation in single nucleon-nucleon collisions and found numerically to be approximately valid for energetic nucleon-nucleon collisions in case of intermediate energy heavy-ion reactions. Primary collision times of nucleons in the dinuclear reaction zone are calculated for various laboratory energies and the approach to local equilibrium is followed in time. Average relaxation times for highly excited finite nuclear systems are found to be considerably shorter than for related infinite nuclear matter problems, however, still too large as to allow for the formation of hot spots in nuclei.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01289571
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  • 10
    Digitale Medien
    Digitale Medien
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1987)
    Springer
    The European physical journal 327 (1987), S. 87-100 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70.-z ; 25.70.Lm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Central collisions of heavy nuclei are investigated within the limit of selfconsistent independent single-particle motion in terms of the Wigner transform of the one-body density matrix in space and time. The energy regime considered extends from roughly 15 MeV/u to 150 MeV/u. Special attention is devoted to the relation between energy and momentum of the nucleons in the collision zone of the two nuclei. An initial average energy-momentum distributionf(k;E) is determined within the fully quantal approach which proves to be vital for our understanding of energetic particle production in the very early stage of the heavy-ion reaction. A comparison with related classical quantities shows the peculiar features of quantum dynamics for finite size fermion systems far from equilibrium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01295254
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