Disappearance of flow and its relevance to nuclear matter physics

Ogilvie, C. A.; Bauer, Wolfgang; Cebra, D.; Clayton, J. C.; Howden, S.; Karn, J.; Nadasen, A.; Molen, A. Vander; Westfall, G. D.; Wilson, W.K.; Winfield, J. S.

doi:10.1103/physrevc.42.r10

Cited by 90 publications

(67 citation statements)

References 13 publications

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“…It has been shown in the simulation of heavy ion reactions that this beam energy called balance energy, E bal , [4,5,6] depends on the nucleon-nucleon (nn) cross-section in the medium as well as on the potential [5,6] [7,12,13,15].…”

Section: Pacs Numbersmentioning

confidence: 99%

Study of balance energy in central collisions for heavier nuclei

2004

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) is obtained in all cases. Our results are in excellent agreement with experimental data which allows us to predict the balance energy for 238 U + 238 U collision around 37-39 MeV/nucleon. PACS numbers:Thirty years ago it was predicted by Scheid and Greiner [1] that in heavy ion reactions the nuclei will be compressed and heated and that this yields for non central reactions to in-plane flow p dir x . More than a decade later, this conjecture was confirmed by the Plastic Ball group [2]. In the following investigations it turned out that this in-plane flow carries information on the nuclear equation of state [3]. If the nuclear equation of state is stiffer, more compressional energy will be stored in semicentral reactions and, when released, more in-plane flow will be given to the nucleons.The maximal density which is reached in a reaction depends on the beam energy as well as on the system size. The lower the beam energy the less is the compression. At very low energies, the repulsive part of the nuclear equation of state, which appears at densities above the normal nuclear matter density, is not tested anymore and the nucleons feel only the attractive mean field. A typical example is the deep inelastic reactions in which the two nuclei rotate around a common center. This rotation creates in-plane flow as well but in opposite direction: Due to the common rotation the nucleons stick together for a while and will be emitted into the direction opposite to the impact parameter whereas the in-plane flow which is caused by compression will be in the direction of the impact parameter.There is a beam energy at which the in-plane flow disappears when changing from the direction into that opposite to the impact parameter. It has been shown in the simulation of heavy ion reactions that this beam energy called balance energy, E bal , [4,5,6] depends on the nucleon-nucleon (nn) cross-section in the medium as well as on the potential [5,6] [7,12,13,15].Apart from the directed in-plane flow, differential as well as elliptic flow has also been predicted very recently [16].The measurements of the balance energy over wide range of system sizes provide an excellent opportunity to pin down the role of the mass dependence, where only preliminary studies [7,10] have been performed yet. These preliminary studies suggest a power law dependence ∝ A τ of the balance energy on the mass number of the system. Interestingly, most of the theoretical studies are done within the Boltzmann-Uehling-Uhlenbeck (BUU) model [4,5,6,7,10,12,15,16,17,18,19,20,21]. Some attempts, however, also exist within the framework of Quantum Molecular Dynamics (QMD) model [13,22,23,24]. Heavy systems are rather rarely analyzed in these approaches.Our present aim is therefore to study the mass dependence of the balance energy in heavy colliding nuclei and to predict for the first time the disappearance of the collective in-plane flow in central 238 U + 238 U collision. We shall show that the mass dependence of E bal for heavier nuclei scales approximately more asra...

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Section: Pacs Numbersmentioning

confidence: 99%

Study of balance energy in central collisions for heavier nuclei

2004

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“…The flow parameter F is by definition the increase of <P x /A> from Y=Y nn (Y r =0.5) to Y=Y proj (Y r =1) by using the slope of the function <P x /A> =f(Y r ) at mid-rapidity [23,24]. It reads:…”

Section: Definitionmentioning

confidence: 99%

Measurements of sideward flow around the balance energy

Cussol¹,

Lefort²,

Péter³

et al. 2002

Phys. Rev. C

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Sideward flow values have been determined with the INDRA multidetector for Ar+Ni, Ni+Ni and Xe+Sn systems studied at GANIL in the 30 to 100 A.MeV incident energy range. The balance energies found for Ar+Ni and Ni+Ni systems are in agreement with previous experimental results and theoretical calculations. Negative sideward flow values have been measured. The possible origins of such negative values are discussed. They could result from a more important contribution of evaporated particles with respect to the contribution of promptly emitted particles at mid-rapidity. But effects induced by the methods used to reconstruct the reaction plane cannot be totally excluded. Complete tests of these methods are presented and the origins of the "auto-correlation" effect have been traced back. For heavy fragments, the observed negative flow values seem to be mainly due to the reaction plane reconstruction methods. For light charged particles, these negative values could result from the dynamics of the collisions and from the reaction plane reconstruction methods as well. These effects have to be taken into account when comparisons with theoretical calculations are done.

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“…Consequently, at energies E = 2µ rel (K = 0) the quantities ImJ α and ImT α (17) vanish. This zero of ImT α is not restricted to the quasiparticle approximation (2) , which can easily be demonstrated by introducing the spectral representation for the full one-particle propagators [20]. In the numerator of eq.…”

Section: The Origin Of the Enhancement In The In-medium Cross Secmentioning

confidence: 99%

“…(2). This form of the Pauli operator takes hole-hole-scattering into account, that is neglected in the usual Brueckner theory taking the Pauli operator as [15].…”

Section: The Derivation Of the In-medium Nucleon-nucleon Cross Sementioning

confidence: 99%

Critical enhancement of the in-medium nucleon-nucleon cross section at low temperatures

1994

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The in-medium nucleon-nucleon cross section is calculated starting from the thermodynamic Tmatrix at finite temperatures. The corresponding Bethe-Salpeter-equation is solved using a separable representation of the Paris nucleon-nucleon-potential. The energy-dependent in-medium N-N cross section at a given density shows a strong temperature dependence. Especially at low temperatures and low total momenta, the in-medium cross section is strongly modified by in-medium effects. In particular, with decreasing temperature an enhancement near the Fermi energy is observed. This enhancement can be discussed as a precursor of the superfluid phase transition in nuclear matter.

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Disappearance of flow and its relevance to nuclear matter physics

Cited by 90 publications

References 13 publications

Study of balance energy in central collisions for heavier nuclei

Study of balance energy in central collisions for heavier nuclei

Measurements of sideward flow around the balance energy

Critical enhancement of the in-medium nucleon-nucleon cross section at low temperatures

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