Pi- / pi+ ratio in heavy ions collisions: Coulomb effect or chemical equilibration?
Aug, 1996
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Abstract:
We calculate the pi-/pi+ ratio for Pb+Pb at CERN/SPS energies and for Au+Au at BNL/AGS energies using a (3+1) dimensional hydrodynamical model. It turns out that it is possible to explain the low m_t enhancement in the ratio observed in experiment without consideration of the Coulomb effect. Our calculations are based on previous (3+1) dimensional hydrodynamical simulations (HYLANDER), which described many other aspects of experimental data. In this model the observed enhancement is a consequence of baryon and strangeness conservation and of chemical equilibration of the system and is caused by the decay of produced hyperons, which leads to a difference in the total number of positive and negative pions as well. We analyse and predict the total multiplicity of hyperons for the different collisions. Based on the same approach, we also present results for the pi-/pi+ ratio for S+S (CERN/SPS) collisions, where we find a similar effect. The absence of the enhancement of the pi-/pi+ ratio in the S+S data presented by the NA44 Collaboration, if confirmed, could indicate that chemical equilibration has not yet been estabilished in this reaction.- scattering: heavy ion
- sulfur
- lead
- gold
- pi-: hadroproduction
- pi+: hadroproduction
- yield: ratio
- hydrodynamics
- fireball
- quantum chromodynamics
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