Modeling Relativistic Heavy Ion Collisions at the Ags

Abstract

A quantitative model, based on hadronic physics and Monte Carlo cascading, is described and applied to heavy ion collisions at BNL-AGS energies (∼ 14 GeV/u). The model was found to be in excellent agreement with particle spectra where data previously existed, for Si beams, and was able to successfully predict the spectra where data were initially absent, for Au beams. For Si + Au collisions, baryon densities of three or four times the normal nuclear matter density (ρ 0 ) are seen in the theory, whereas for Au + Au collisions, matter at densities up to 10 ρ 0 is anticipated. The possibility that unusual states of matter may be created by the Au beams and potential signatures for its observation are considered.

Strangeness production in the HSD transport approach from SIS to SPS energies

“…Whereas the proton stopping is reasonably well reproduced by the calculation the pion spectra again clearly come out too broad in rapidity as compared to the experimental data. The overestimate of pions in the HSD approach in Si + Au collision is in agreement with the findings within the RQMD model [28] and the ARC model [13]. Thus the experimentally observed strong reduction in the width of the pion rapidity spectra in heavy-ion collisions compared to p + p collisions at AGS energies, already observed in the light system Si + Al, seems to be a general problem for microscopic hadronic models.…”

“…6 of Ref. [28]) and with the ARC model [13]. Both observables, the strong enhancement of the scaled kaon yield as well as the lowering of the width of the pion rapidity distribution, are already found for the rather light system Si + Al (see Fig.…”

“…Our findings have to be compared to results obtained by other microscopic approaches. At AGS energies there exist calculations from RQMD within different versions [19,28] and from ARC [13] for the system Si + Au. The earlier RQMD and ARC models agree with the presented results concerning the overestimation of the pion yield.…”

Neutral pions and η mesons as probes of the hadronic fireball in nucleus-nucleus collisions around1AGeV

“…Under these conditions the onset of the partial restoration of chiral symmetry, which is a fundamental symmetry of quantum chromodynamics, could manifest itself in modifications of hadron properties inside the fireball. At beam energies of ≈10A GeV, as they are available at the AGS accelerator facility at BNL (Brookhaven), even higher baryon densities and temperatures are reached in the initial stage of the fireball [9]. In addition to the chiral phase transition one may approach in those collisions already the phase transition from a hadron gas to a quark-gluon plasma due to the deconfinement of quarks and gluons.…”

Ultrarelativistic cascades and strangeness production

“…It is not possible to ignore the time structure of the elementary collisions nor the nature of the objects produced in the initial particle-particle collisions, and which then partake in ensuing collisions. At AGS momenta [7], -1.0 -5GeV/c, the introduction of the most evident, lowest lying resonances, the A, the N* and the p , was often sufficient for a reasonably accurate picture of the dynamics. The essential time structure for a many body collision was then set by the resonance lifetimes, all N 1.5 fm/c.…”