The importance of multiparticle collisions in heavy ion reactions

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The importance of multiparticle collisions in
heavy ion reactions
Johann Wolfgang Goethe-Universität
Frankfurt Institut für Theoretische Physik

• C. Greiner
• Zimanyi 75 Memorial Workshop
• Budapest, july 2007

• Motivation chemical equilibrium of anti-baryons
• Chemical equilibration at the Hagedorn
  temperature
• Thermalization and viscosity at RHIC by
• Outlook

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Exploring the phases of nuclear matter
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Strangeness production at SpS energies
Production of Antihyperons QGP signature?
J. Geiss
P. Koch, B. Müller, J. Rafelski
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Production of Anti-Baryons
Multimesonic channels
R.Rapp and E. Shuryak, Phys.Rev.Lett.86 (2001)
2980
C.Greiner and S.Leupold, J.Phys. G27 (2001) L95
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C.Greiner, AIP Conf. Proc. 644337 (2003)
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production at RHIC
Thermal rates within chiral SU(3) description
Chemical population of baryons / anti-baryons
I. Shovkovy, J. Kapusta
P. Huovinen, J. Kapusta
Insufficient by a factor of 3 to 4
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Chemical Freeze-out and of QCD
(P. Braun-Munzinger, J. Stachel, C. Wetterich,
Phys.Lett.B59661-69 (2004))

• Hadronic resonance gas
• vs. lattice

Chemical equilibration of baryon / anti-baryons
Multimesonic channels
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Possible solution by Hagedorn states
C. Greiner, P. Koch, F. Liu, I. Shovkovy, H.
Stöcker J.Phys.G31 (2005)
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Hagedorn gas close to

• Hagedorn spectrum

• Hagedorn like excitations
• in transport models

RQMD
HSD
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Estimate for baryon/antibaryon production
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Microcanonical decay of HS
(Fuming Liu)
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Master Equations for the decay

• master equation

J. Noronha-Hostler, C. Greiner, I. A. Shovkovy.
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Results np HS np

• Case 1 Pions are held in equilibrium
• Case 2 Hagedorn States are held in equilibrium,
  when there are no initial pions
• when they are close to equilibrium

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Results np HS np

• Case 3 Both are out of equilibrium
• Quasi-equilibrium is first reached when both the
  heaviest resonance and the pions have exceeded
  their respective equilibration times, and
  t2GeV0.2 fm/c and tp0.2 to 0.02 fm/c . Full
  quasi-equilibrium is reached when the lightest
  resonance reaches quasi-equilibrium i.e.
  t7GeV0.8 fm/c.
• Total equilibration time

J. Noronha-Hostler, C. Greiner, I. A. Shovkovy.
(In preparation)
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Results np HS np
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Results Expansion
J. Noronha-Hostler, C. Greiner, I. A. Shovkovy.
(In Preparation)
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The strange sector of baryons/antibaryons
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Importance of baryonic HS CBM?
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The order and shape of QGP phase transition
I. Zakout, CG and J. Schaffner-Bielich, NPA 781
(2007) 150
density of states
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Relativistic Quantum Transport for URHIC
RHIC, LHC

• microscopic transport calculations of partonic
  degrees of freedom

new development
Boltzmann Approach of MultiParton Scatterings
(BAMPS)
Z. Xu and C. Greiner, PRC 71, 064901 (2005)
collision probability
D3x
particle in cell method
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Initial production of partons
minijets
string matter
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fast isotropization and thermalisation
elliptic flow in noncentral AuAu collisions at
RHIC
Z. Xu and C. Greiner, hep-ph/0703233
Z. Xu and C. Greiner, NPA 774, 787 (2006)
central
hydrodynamical evolution of momentum spectrum,
micr. determination of transport parameter
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Comparison with RHIC data
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Evolution of temperature and spectrum with CGC
initial condition
Andrej El
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extracting the viscosity
preliminary
Bjorken geometry
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Conclusions and Outlook

• Potential Hagedorn states as additional dof can
  explain and also strange baryon
  production close to
• (re-)population and decay are governed by
  detailed balance
• Three main assumptions
• (1)
• (2)
• (3) microcanonical statistical decay
• Multiparticle interactions also important for
  very high energies ( )
• Future Embedding into UrQMD

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Parameters

• Branching Ratios using a Gaussian
  distribution
• where ltngt0.91.2(mi/mp)3 to 9 and
  s20.5(mi/mp) 21 to 12
• The decay width is then Gi0.15mi-60250 to
  1000 MeV
• ltnbgt0.50.6(mi/mp)3 to 6 and
  Gi,pGi-ltBgtGi,BB where Gi,BB ltBgtGi. Since ltBgt
  ranges from 0.2 to 0.4, Gi,BB is between 50 and
  400 MeV.
• Bjorken expansion for r07.1 and a00.05

-F.M. Liu et. al.
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parton scatterings in leading order pQCD
J.F.Gunion, G.F.Bertsch, Phys. Rev. D 25,
746(1982)
screening mass
LPM suppression the formation time