Mass Dependence of Directed Collective Flow

  • M. J. Huang
  • R. C. Lemmon
  • F. Daffin
  • W. G. Lynch


The determination of the equation of state of nuclear matter is one of the main objectives of relativistic heavy-ion physics. Insight into the equation of state has been gained through the study of collective phenomena, which can be attributed to the response of hot and dense nuclear matter from the hot and dense region formed by the overlap of projectile and target nuclei [1, 2]. In particular, directed sidewards flow is considered as an important signature of nuclear compression and thus is sensitive to the nuclear equation of state. The sidewards direction of the flow was described years ago on the basis of macroscopic thermaldynamic/hydrodynamical picture [3] and the more microscopic cascade model [4]. As two nuclei collide, the pressure and density increase in the interaction region. At a finite impact parameter there is an inherent asymmetry in the pressure, which results in a transverse flow of matter in the direction of lowest pressure. The amount of transverse flow is directly related to the stiffness of the nuclear equation of state and transport properties of the nuclear medium [5]. This flow reflects the interplay of collective and random motions. For a thermalized system, the random motions of emitted fragments are dictated by the thermal energy, which is independent of mass. Contributions to the fragment energy due to collective motion, on the other hand, increase linearly with mass, making the flow more easily observed for heavier fragments [6, 7].


Transverse Momentum Impact Parameter Mass Dependence Momentum Dependence Reaction Plane 
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Copyright information

© Springer Science+Business Media New York 1996

Authors and Affiliations

  • M. J. Huang
    • 1
  • R. C. Lemmon
    • 1
  • F. Daffin
    • 1
  • W. G. Lynch
    • 1
  1. 1.National Superconducting Cyclotron LaboratoryMichigan State UniversityEast LansingUSA

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