8 research outputs found
Anisotropic flow at RHIC: How unique is the number-of-constituent-quark scaling?
The transverse momentum dependence of the anisotropic flow for ,
, nucleon, , and is studied for Au+Au collisions at
GeV within two independent string-hadron transport
approaches (RQMD and UrQMD). Although both models reach only 60% of the
absolute magnitude of the measured , they both predict the particle type
dependence of , as observed by the RHIC experiments: exhibits a
hadron-mass hierarchy (HMH) in the low region and a
number-of-constituent-quark (NCQ) dependence in the intermediate region.
The failure of the hadronic models to reproduce the absolute magnitude of the
observed indicates that transport calculations of heavy ion collisions at
RHIC must incorporate interactions among quarks and gluons in the early, hot
and dense phase. The presence of an NCQ scaling in the string-hadron model
results suggests that the particle-type dependencies observed in heavy-ion
collisions at intermediate might be related to the hadronic cross
sections in vacuum rather than to the hadronization process itself.Comment: 10 pages, 5 figures; A new author (H. Petersen) is added; A new
figure (fig.1) on time evolution of elliptic flow and number of collisions is
added; Version accepted for publication in J. Phys.
Nonequilibrium models of relativistic heavy-ion collisions
To be published in J. Phys. G - Proceedings of SQM 2004 : We review the results from the various hydrodynamical and transport models on the collective flow observables from AGS to RHIC energies. A critical discussion of the present status of the CERN experiments on hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A.GeV: here the hydrodynamic model has predicted the collapse of the v2-flow ~ 10 A.GeV; at 40 A.GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as evidence for a first order phase transition at high baryon density r b. Moreover, the connection of the elliptic flow v2 to jet suppression is examined. It is proven experimentally that the collective flow is not faked by minijet fragmentation. Additionally, detailed transport studies show that the away-side jet suppression can only partially (< 50%) be due to hadronic rescattering. Furthermore, the change in sign of v1, v2 closer to beam rapidity is related to the occurence of a high density first order phase transition in the RHIC data at 62.5, 130 and 200 A.GeV