Freeze-out mechanism and phase-space density in ultrarelativistic heavy-ion collisions

We explore the consequences of a freeze-out criterion for heavy-ion collisions, based on pion escape probabilities from the hot and dense but rapidly expanding collision region. The influence of the expansion and the scattering rate on the escape probability is studied. The temperature dependence of this scattering rate favors a low freeze-out temperature of $\ensuremath{\sim}100\mathrm{MeV}.$ In general, our results support freeze-out along finite four-volumes rather than sharp three-dimensional hypersurfaces, with high-${p}_{\ensuremath{\perp}}$ particles decoupling earlier from smaller volumes. We compare our approach to the proposed universal freeze-out criteria using the pion phase-space density and its mean free path.

[1]  S. Pratt.  Correlations and fluctuations, a summary of Quark Matter 2002 , 2003, nucl-th/0308022.

[2]  K. Filimonov,et al.  Universal pion freeze-out in heavy-ion collisions. , 2003, Physical review letters.

[3]  U. Heinz,et al.  Reconstructing the Freeze-out State in Pb+Pb Collisions at 158 A GeV/ c a , 1999, nucl-th/9907096.

[4]  E. al.,et al.  One-, two-, and three-particle distributions from 158A GeV/c central Pb+Pb collisions , 2002, nucl-ex/0210002.

[5]  E. al.,et al.  Energy dependence of pion and kaon production in central Pb+Pb collisions , 2002, nucl-ex/0205002.

[6]  Y. Sinyukov,et al.  Freeze-out problem in hydrokinetic approach to A + A collisions. , 2002, Physical review letters.

[7]  T. C. Sangster,et al.  Centrality Dependence ofπ+/−,K+/−,p, andp¯Production fromsNN=130GeVAu + Au Collisions at RHIC , 2001, nucl-ex/0112006.

[8]  U. Heinz,et al.  Flow effects on the freeze-out phase-space density in heavy-ion collisions , 2001, nucl-th/0108051.

[9]  B. Lukács,et al.  Simple solutions of fireball hydrodynamics for self-similar, ellipsoidal flows , 2000, hep-ph/0012127.

[10]  M. Murray.  Anti)proton and pion source sizes and phase space densities in heavy ion collisions , 2000, nucl-ex/0008006.

[11]  S. Padula,et al.  Continuous emission versus freeze-out via hanbury brown-twiss , 2000, hep-ph/0002275.

[12]  J. Cramer,et al.  Universal pion freeze-out phase-space density , 1999, hep-ph/9902342.

[13]  T. Kodama,et al.  Particle emission in the hydrodynamical description of relativistic nuclear collisions , 1996 .

[14]  Hayes,et al.  Review of Particle Physics. , 1996, Physical review. D, Particles and fields.

[15]  M. Vassiliou,et al.  Two-pion Bose-Einstein correlations in nuclear collisions at 200 GeV per nucleon , 1995 .

[16]  R. Venugopalan,et al.  Non-equilibrium properties of hadronic mixtures , 1993 .

[17]  Heinz,et al.  Relativistic hydrodynamics in a global fashion. , 1993, Physical review. C, Nuclear physics.

[18]  H. Bebie,et al.  The Role of the entropy in an expanding hadronic gas , 1992 .

[19]  P. Lichard,et al.  Dependence ofJ/Ψ suppression in heavy ion collisions on total transverse energy, nucleon numbers andJ/Ψ transverse momentum , 1989 .

[20]  S. Nagamiya.  Role of Mean Free Paths of Product Particles in High-Energy Nucleus-Nucleus Collisions , 1982 .

[21]  J. Bondorf,et al.  A Simple Analytic Hydrodynamic Model for Expanding Fireballs , 1978 .

[22]  Fred Cooper,et al.  Single-particle distribution in the hydrodynamic and statistical thermodynamic models of multiparticle production , 1974 .

[23]  Irene A. Stegun,et al.  Handbook of Mathematical Functions. , 1966 .