Chemical Equilibration in Relativistic Heavy Ion Collisions

Abstract

In the hadronic sector of relativistic heavy ion physics, the $\rho <=>2\pi$ reaction is the strongest one, strong enough to equilibrate the $\rho$ with the pions throughout the region from chemical freezeout to thermal freezeout when free-particle interactions (with no medium-dependent effects) are employed. Above the chiral restoration temperature, only $\rho$'s and $\pi$'s are present, in that the chirally restored $A_1$ is equivalent to the $\rho$ and the mesons have an SU(4) symmetry, with no dependence on isospin and negligible dependence on spin. In the same sense the $\sigma$ and $\pi$ are "equivalent" scalars. Thus the chirally restored $\rho \leftrightarrows 2\pi$ exhaust the interspecies transitions. We evaluate this reaction at $T_c$ and find it to be much larger than below $T_c$, certainly strong enough to equilibrate the chirally restored mesons just above $T_c$. When emitted just below $T_c$ the mesons remain in equilibrium, at least in the chiral limit because of the Harada-Yamawaki "vector manifestation" that requires that mesonic coupling constants go to zero (in the chiral limit) as $T$ goes to $T_c$ from below. Our estimates in the chiral limit give deviations in some particle ratios from the standard scenario (of equilibrium in the hadronic sector just below $T_c$) of about double those indicated experimentally. This may be due to the neglect of explicit chiral symmetry breaking in our estimates. We also show that the instanton molecules present above $T_c$ are the giant multipole vibrations found by Asakawa, Hatsuda and Nakahara and of Wetzorke et al. in lattice gauge calculations. Thus, the matter formed by RHIC can equivalently be called: chirally restored mesons, instanton molecules, or giant collective vibrations. It is a strongly interacting liquid.

41 pages, 15 figures, v2) Appendix C added

References in corpus (25)

• Hadron production in Au-Au collisions at RHIC
• Hidden Local Symmetry at Loop -- A New Perspective of Composite Gauge Boson and Chiral Phase Transition
• Heavy Quark Anti-Quark Free Energy and the Renormalized Polyakov Loop
• Behavior of Charmonium Systems after Deconfinement
• Lattice Results on QCD Thermodynamics
• Chiral Restoration in Hot and/or Dense Matter
• Thermodynamics at Non-Zero Baryon Number Density: A Comparison of Lattice and Hadron Resonance Gas Model Calculations
• Chemical Freeze-out and the QCD Phase Transition Temperature
• Rethinking the Properties of the Quark-Gluon Plasma at $T\sim T_c$
• rho^0 Production and Possible Modification in Au+Au and p+p Collisions at sqrt(s_NN) = 200 GeV
• Collision geometry scaling of Au+Au pseudorapidity density from sqrt(s_NN) = 19.6 to 200 GeV
• Double Decimation and Sliding Vacua in the Nuclear Many-Body System
• Matter-induced modification of resonances at RHIC freezeout
• Temporal quark and gluon propagators: measuring the quasiparticle masses
• Spectral function and excited states in lattice QCD with maximum entropy method
• Heavy quark free energies and the renormalized Polyakov loop in full QCD
• Meson Spectral Functions at finite Temperature
• The \bar q q Bound States and Instanton Molecule at T >~ T_c
• Pi+ Pi- Emission in High-Energy Nuclear Collisions
• Understanding the Strong Coupling Limit of the $\mathcal{N}=4$ Supersymmetric Yang-Mills at Finite Temperature
• Thermal analysis of production of resonances in relativistic heavy-ion collisions
• Matching the QCD and Hadron Sectors and Medium Dependent Meson Masses; Hadronization in Relativistic Heavy Ion Collisions
• Nature of the Chiral Restoration Transition in QCD
• A New State Of Hadronic Matter At High Density
• $\rho (770{)}^0$, K${}^{\ast }(892{)}^0$ and f${}_0(980)$ Production in Au-Au and pp Collisions at $\sqrt{s_{NN}}$ = 200 GeV

Cited by in corpus (20)

• Static quark anti-quark interactions in zero and finite temperature QCD. I. Heavy quark free energies, running coupling and quarkonium binding
• The hot non-perturbative gluon plasma is an almost ideal colored liquid
• From Kadanoff-Baym dynamics to off-shell parton transport
• Dynamical quasiparticles properties and effective interactions in the sQGP
• QCD thermodynamics and confinement from a dynamical quasiparticle point of view
• Shear Viscosity to Entropy Density Ratio of QCD below the Deconfinement Temperature
• QCD Viscosity to Entropy Density Ratio in the Hadronic Phase
• The \bar q q Bound States and Instanton Molecule at T >~ T_c
• Isotropization far from equilibrium
• Thermal Dilepton Production from Dropping rho based on the Vector Manifestation
• Matter formed at the BNL relativistic heavy ion collider
• Static quark anti-quark free and internal energy in 2-flavor QCD
• Vector-axialvector mixing from a chiral effective field theory at finite temperature
• STAR ${\rho }^0/{\pi }^{-}$ Ratio in Au-Au Peripheral Collisions at RHIC and the Vector Manifestation of Hidden Local Symmetry
• Running coupling of 2-flavor QCD at zero and finite temperature
• The Problem of Mass: Mesonic Bound States Above T_c
• Thermal Dilepton Production from Dropping rho in the Vector Manifestation
• An Effective Field Theory at Finite Density
• A new state of matter at high temperature as "sticky molasses"
• Chiral Symmetry of Heavy-Light-Quark Hadrons in Hot/Dense Matter