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
• The Physics of High Baryon Density
• IPHC Strasbourg, Sept. 2006

• Motivation chemical equilibration of
  anti-baryons
• Equilibration by potential Hagedorn states
• Thermalization 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 HS?npBaB
dNR(i)/dt-GiNR(i)ånGi,p lt i,n(T) (Np)nBi!
npGi,BaBlti,ltngtBaB (T)(Np )ltngt N2BaB
dNp /dtåi ånGi,pnBi! np(NR(i)-lt (T) (Np )n)åi
Gi,BaBltngt(NR(i)-lti,ltngtBaB(T)(Np )ltngtN2BaB)
dNBaB/dt-åiGi,BaB(NBaB2 Npltngt lt i,ltngt(T)-NR(i))
J. Noronha-Hostler
TexPoint fonts used in EMF AAAAAAA
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Considering the decay HS?np
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HS?npBaB
Np (t0)Equilibrium NRes(t0)0
Np (t0) Equilibrium NRes(t0)Equilibrium
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HS?npBaB when the Hagedorn Resonances start at
twice equilibrium values and the rest starts at
zero.
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HS?npBaB when the Hagedorn Resonances start at
twice equilibrium values and the rest starts at
equilibrium.
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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
nucl-th/0605052, I. Zakout, CG and J.
Schaffner-Bielich
density of states
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Thermalization at RHIC
elliptic flow --- early signature of QGP
evidence for an early buildup of pressure and a
fast thermalization of the quark-gluon system

• How can one describe the fast thermalization by
  the partonic collisions?
• How can one understand the hydrodynamical
  behavior by the partonic collisions?

transport simulation on-shell parton cascade
Z. Xu and C. Greiner, PRC 71, 064901 (2005)
solving the Boltzmann-equations for quarks and
gluons
new development
(Z)MPC, VNI/BMS
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Initial production of partons
minijets
string matter
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Stochastic algorithm
P.Danielewicz, G.F.Bertsch, Nucl. Phys. A 533,
712(1991) A.Lang et al., J. Comp. Phys. 106,
391(1993)
cell configuration in space
D3x
for particles in D3x with momentum p1,p2,p3 ...
collision probability
parton scatterings in leading order pQCD
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the central region h -0.50.5 and
xt lt 1.5 fm
including gglt-gtggg
without gglt-gtggg
thermalization and hydrodynamical behavior
NO thermalization and free
streaming
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transverse energy at y0 in AuAu central
collision
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elliptic flow in noncentral AuAu collisions at
RHIC
peripheral
central
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Comparison with RHIC data
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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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Nonequilibrium dilepton production
(B. Schenke)
Spectral function of the ?-meson
CERES
? quantum off-shell-transport description
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Non-equilibrium dilepton production rate
Contributions to the rate at time t at constant
energy ?
Evolving spectral function and
dilepton rate
B. Schenke, C. Greiner, Phys.Rev.C73034909
(2006)
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Dilepton yields from fireball
(B. Schenke)
Dropping mass (linearly in time) and resonance
coupling scenarios for k0
Dropping mass scenario integrated over momenta
B. Schenke, C. Greiner, Phys.Rev.C73034909
(2006)
B. Schenke, C. Greiner, arXivhep-ph/0608032
(2006)
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