The importance of multiparticle collisions in heavy ion reactions - - PowerPoint PPT Presentation

The importance of multiparticle collisions in heavy ion reactions

• C. Greiner

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

Johann Wolfgang Goethe-Universität Frankfurt Institut für Theoretische Physik

• Motivation: chemical equilibration of anti-baryons
• Equilibration by potential Hagedorn states
• Thermalization at RHIC by
• Outlook

Exploring the phases of nuclear matter

Strangeness production at SpS energies

• J. Geiss

Production of Antihyperons: QGP signature…?

• P. Koch, B. Müller, J. Rafelski

Production of Anti-Baryons

R.Rapp and E. Shuryak, Phys.Rev.Lett.86 (2001) 2980 C.Greiner and S.Leupold, J.Phys. G27 (2001) L95

Multimesonic channels

C.Greiner, AIP Conf. Proc. 644:337 (2003)

production at RHIC

• I. Shovkovy, J. Kapusta

Thermal rates within chiral SU(3) description Chemical population of baryons / anti-baryons:

• P. Huovinen, J. Kapusta

Insufficient by a factor of 3 to 4

Chemical Freeze-out and of QCD

Hadronic resonance gas

• vs. lattice:

(P. Braun-Munzinger, J. Stachel, C. Wetterich, Phys.Lett.B596:61-69 (2004))

Chemical equilibration

• f baryon / anti-baryons:

Multimesonic channels:

Possible solution by Hagedorn states

• C. Greiner, P. Koch, F. Liu,
• I. Shovkovy, H. Stöcker

J.Phys.G31 (2005)

• K. Redlich et al, K. Bugaev et al

Hagedorn gas close to

• Hagedorn spectrum:
• Hagedorn like excitations

in transport models: RQMD HSD

Estimate for baryon/antibaryon production

Microcanonical decay of HS

(Fuming Liu)

Master Equations for the decay HS→nπ+BaB

• J. Noronha-Hostler

dNR(i)/dt=-ΓiNR(i)+∑nΓi,π < i,n(T) (Nπ)nBi! nπ+Γi,BaB<i,<n>BaB (T)(Nπ )<n> N2

BaB

dNπ /dt=∑i ∑nΓi,πnBi! nπ(NR(i)-< (T) (Nπ )n)+∑i Γi,BaB<n>(NR(i)-<i,<n>BaB(T)(Nπ )<n>N2

BaB)

dNBaB/dt=-∑iΓi,BaB(NBaB

2 Nπ <n> < i,<n>(T)-NR(i))

Considering the decay HS→nπ

HS→nπ+BaB

Nπ (t=0)=Equilibrium NRes(t=0)=0 Nπ (t=0) =Equilibrium NRes(t=0)=Equilibrium

HS→nπ+BaB when the Hagedorn Resonances start at

twice equilibrium values and the rest starts at zero.

HS→nπ+BaB when the Hagedorn Resonances start at

twice equilibrium values and the rest starts at equilibrium.

The strange sector of baryons/antibaryons

Importance of baryonic HS CBM?

The order and shape of QGP phase transition

nucl-th/0605052, I. Zakout, CG and J. Schaffner-Bielich

) 4 ( ~ ) , (

] [

) 2 (

Bv m e m c v m

B H T m

−

+ −

δ ρ

α

density of states:

}

4 1 + = α γ

) (

B

µ α

Thermalization at RHIC

elliptic flow --- `early signature´ of QGP

...) 2 cos 2 cos 2 1 (

2 1

1

2 2

+ + +

=

φ φ

π φ

v v

dy dp dN dyd dp dN

T h T h

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?

) , ( ) , ( ) , ( p x C p x C p x f p

ggg gg gg gg ↔ ↔

+ = ∂ µ

µ

transport simulation: on-shell parton cascade

solving the Boltzmann-equations for quarks and gluons

new development

(Z)MPC, VNI/BMS

• Z. Xu and C. Greiner, PRC 71, 064901 (2005)

Initial production of partons

dt d p x f x p x f x K dy dy dp d

cd ab t b t a d c b a t jet →

∑

= σ σ ) , ( ) , (

2 2 2 2 1 1 , ; , 2 1 2

minijets string matter

Stochastic algorithm

P.Danielewicz, G.F.Bertsch, Nucl. Phys. A 533, 712(1991 A.Lang et al., J. Comp. Phys. 106, 391(1993)

for particles in ∆3x with momentum p1,p2,p3 ...

collision probability:

2 3 3 2 1 32 32 3 23 23 3 22 22

) ( 8 2 3 3 2 2 2 x t E E E I P for x t v P for x t v P for

rel rel

∆ ∆ = → ∆ ∆ = → ∆ ∆ = ↔ σ σ

( ) 2 ( 2 ) 2 ( 2 ) 2 ( 2 1

2 ' 1 3 2 1 ) 4 ( 4 2 ' 2 ' 1 123 ' 2 3 ' 2 3 ' 1 3 ' 1 3 32

p p p p p M E p d E p d I − − + + = ∫

→

δ π π π

cell configuration in space ∆3x

( )

LPM D D ggg gg D gg gg

m q k k q g m q s g M m q s g M Θ         + −         + = + =

⊥ ⊥ ⊥ ⊥ ⊥ → ⊥ → 2 2 2 2 2 2 2 2 2 4 2 2 2 2 2 4 2

) ( 12 ) ( 2 9 , ) ( 2 9  

parton scatterings in leading order pQCD

the central region: η: [-0.5:0.5] and xt < 1.5 fm

thermalization and hydrodynamical behavior NO thermalization and free streaming including gg<−>ggg without gg<−>ggg

transverse energy at y=0 in Au+Au central collision

elliptic flow in noncentral Au+Au collisions at RHIC:

central peripheral

Comparison with RHIC data

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

CERES

Nonequilibrium dilepton production

Spectral function of the ρ-meson: free ρ in-medium

→ quantum “off-shell”-transport description

(B. Schenke)

Non-equilibrium dilepton production rate:

Evolving spectral function and dilepton rate Contributions to the rate at time τ at constant energy ω

• B. Schenke, C. Greiner, Phys.Rev.C73:034909 (2006)

Dilepton yields from fireball

(B. Schenke)

0.0 0.2 0.4 0.6 0.8 1.0 0.5 1.0 1.5 2.0 2.5 3.0

dN/dM [10

• 3 GeV
• 1]

M [GeV]

Dynamic Markov

Dropping mass scenario integrated over momenta: Dropping mass (linearly in time) and resonance coupling scenarios for k=0:

• B. Schenke, C. Greiner, Phys.Rev.C73:034909 (2006)
• B. Schenke, C. Greiner, arXiv:hep-ph/0608032 (2006)