Transition from Baryon- to Meson-Dominated Freeze Out -- Early Decoupling around 30 A GeV?

Abstract

The recently discovered sharp peak in the excitation function of the K+/pi+ ratio around 30 A GeV in relativistic heavy-ion collisions is discussed in the framework of the Statistical Model. In this model, the freeze-out of an ideal hadron gas changes from a situation where baryons dominate to one with mainly mesons. This transition occurs at a temperature T = 140 MeV and baryon chemical potential mu(B) = 410 MeV corresponding to an energy of sqrt(s) = 8.2 GeV. The calculated maximum in the K+/pi+ ratio is, however, much less pronounced than the one observed by the NA49 Collaboration. The smooth increase of the K-/pi- ratio with incident energy and the shape of the excitation functions of the Lambda/pi+, Xi-/pi+ and Omega/pi ratios all exhibiting maxima at different incident energies, is consistent with the presently available experimental data. The measured K+/pi+ ratio exceeds the calculated one just at the incident energy when the freeze-out condition is changing. We speculate that at this point freeze-out might occur in a modified way. We discuss a scenario of an early freeze-out which indeed increases K+/pi+ ratio while most other particle ratios remain essentially unchanged. Such an early freeze-out is supported by results from HBT studies.

arXiv comment8 pages, 5 figures, SQM2006 conference, Los Angeles, March 2006

References in corpus (17)

• Energy Dependence of Pion and Kaon Production in Central Pb+Pb Collisions
• Unified Description of Freeze-Out Parameters in Relativistic Heavy Ion Collisions
• Maximum Relative Strangeness Content in Heavy Ion Collisions Around 30 A.GeV
• Excitation Function of K${}^{+}$ and ${\pi }^{+}$ Production in Au+Au Reactions at 2-10 AGeV
• Charged Pion Production in 2 to 8 AGeV Central Au+Au Collisions
• Influence of Impact Parameter on Thermal Description of Relativistic Heavy Ion Collisions at GSI/SIS
• An Excitation Function of K${}^{-}$ and K${}^{+}$ Production in Au+Au Reactions at the AGS
• Report from NA49
• $\Lambda$ and $\bar{\Lambda }$ Production in Central Pb-Pb Collisions at 40, 80, and 158 A$\cdot$GeV
• Universal Pion Freeze-out in Heavy-Ion Collisions
• Centrality Dependence of Kaon Yields in Si+A and Au+Au Collisions at Relativistic Energies
• Status of Chemical Freeze-Out
• Review of Results from the NA49 Collaboration
• Relativistic Nucleus-Nucleus Collisions: from the BEVALAC to RHIC
• Strange Meson Enhancement in PbPb Collisions
• Comparison of Strangeness Production between A+A and p+p Reactions from 2 to 160 AGeV
• Review of Nuclear Reactions at the AGS

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