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  • 1985-1989  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1988)
    Springer
    The European physical journal 329 (1988), S. 471-485 
    Details
    ISSN: 1434-601X
    Keywords: 24.10.-i ; 25.70.-z ; 25.70.Jj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The emission of nucleons in central collisions of mass symmetric and asymmetric systems in the intermediate energy regime is investigated within a quantal phase-space approach including mean field as well as two-body collision dynamics. The very energetic tails of the particle spectra are found to originate from high momentum components of the nuclear wave function as well as from successive two-body scattering. Furthermore, the angular distribution of energetic light particles for mass symmetric systems turns out to depend on the effective nucleon-nucleon cross section in the nuclear medium and might be used to determine this quantity experimentally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294352
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1988)
    Springer
    The European physical journal 331 (1988), S. 439-449 
    Details
    ISSN: 1434-601X
    Keywords: 24.10.Cn ; 24.10.-i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We derive a transport equation for the description of non-relativistic heavy-ion collisions from time-dependentG-matrix theory. The approximations introduced are investigated within a modified Lipkin model on theA-body level and by one-dimensional calculations for colliding finite fermion systems on the two-body level. Both approximations are found to hold reasonably well. The classical limit of these equations in phase space yields a transport equation of the Vlasov-Uehling-Uhlenbeck type without double counting of interactions and uniquely determines the time-dependent mean field as well as an in-medium nucleon-nucleon cross-section on the basis of the sameG-matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01291902
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1987)
    Springer
    The European physical journal 327 (1987), S. 87-100 
    Details
    ISSN: 1434-601X
    Keywords: 25.70.-z ; 25.70.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01295254
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1987)
    Springer
    The European physical journal 327 (1987), S. 447-460 
    Details
    ISSN: 1434-601X
    Keywords: 25.70.-z ; 25.70.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01289571
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  • 5
    Electronic Resource
    Electronic Resource
    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
    Keywords: 24.10.Cn ; 24.10.−i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01289628
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamical aspects of intermediate-energy nucleus-nucleus collisions (1988)
    Springer
    The European physical journal 329 (1988), S. 487-495 
    Details
    ISSN: 1434-601X
    Keywords: 24.10.-i ; 25.70.-z ; 25.80.Ls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294353
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    A quantal toy model for heavy-ion collisions (1987)
    Springer
    The European physical journal 326 (1987), S. 21-31 
    Details
    ISSN: 1434-601X
    Keywords: 25.70.−z ; 25.70.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294567
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Quark deconfinement in a semiclassical string-bag model (1987)
    Springer
    The European physical journal 327 (1987), S. 243-249 
    Details
    ISSN: 1434-601X
    Keywords: 11.15Kc ; 12.35Ht ; 12.40Qq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284447
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Microscopic investigations of pion production in heavy-ion collisions (1987)
    Springer
    The European physical journal 326 (1987), S. 97-106 
    Details
    ISSN: 1434-601X
    Keywords: 25.70−z ; 25.90+k ; 13.75 Gx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294576
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    Paper (German National Licenses)
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