Hadronic Rescattering Effects after Hadronization of QGP Fluids

1
Hadronic Rescattering Effects after Hadronization
of QGP Fluids
Workshop Hadronization in 2006 RHIC AGS
annual users meeting

• Tetsufumi Hirano
• Institute of Physics, University of Tokyo

2
Two Topics

• Hadronic Rescattering Effects after Hadronization
  of QGP fluids
• T.Hirano, U.Heinz, D.Kharzeev, R.Lacey, Y.Nara,
  PLB636(2006)299 (in preparation).
• Hadronization through Jet-Fluid Strings
• T.Hirano,M.Isse,A.Ohnishi,Y.Nara,K.Yoshino, (in
  preparation).

3
(CGC )QGP HydroHadronic Cascade
TH et al.(05-)
Hadronic Corona (Cascade, JAM)
t
sQGP core (Full 3D Ideal Hydro)
0.6fm/c
z
0
(Option) Color Glass Condensate
c.f. Similar approach by Nonaka (talk in perfect
fluid workshop)
4
Hydro Meets Data for the First Time at RHIC
Current Three Pillars
THGyulassy(06),TH,Heinz,Kharzeev,Lacey,Nara(06)

• Perfect Fluid (s)QGP Core
• Ideal hydro description of the QGP phase
• Necessary to gain integrated v2
• Dissipative Hadronic Corona
• Boltzmann description of the hadron phase
• Necessary to gain enough radial flow
• Necessary to fix particle ratio dynamically
• Glauber Type Initial Condition
• Diffuseness of initial geometry

A Lack of each pillar leads to discrepancy!
5
(1) Glauber and (2) CGC Hydro Initial Conditions
Which Clear the First Hurdle
Centrality dependence
Rapidity dependence

• Glauber model
• NpartNcoll 8515
• CGC model
• Matching I.C. via e(x,y,h)

6
pT Spectra for identified hadronsfrom QGP
HydroHadronic Cascade
dN/dy and dN/dpT are o.k. by hydrocascade.
Caveat Other components such as recombination
and fragmentation should appear in the
intermediate-high pT regions.
7
v2(Npart) from QGP Hydro Hadronic Cascade
TH et al.(06)

• Glauber
• Early thermalization
• Mechanism?
• CGC
• No perfect fluid?
• Additional viscosity
• is required in QGP

Result of JAM Courtesy of M.Isse
Importance of better understanding of initial
condition
8
Large Eccentricity from CGC Initial Condition
Talk by Y.Nara in Interaction btw hard probes
and the bulk.
Hirano and Nara(04), Hirano et al.(06) Kuhlman
et al.(06), Drescher et al.(06)
y
x
Pocket formula (ideal hydro) v2 0.2e _at_ RHIC
energies
Ollitrault(92)
9
v2(pT) for identified hadronsfrom QGP Hydro
Hadronic Cascade
Glauber type initial condition
CGC initial condition
20-30
20-30
Mass dependence is o.k.
v2(model) gt v2(data)
10
Summary So Far

• An answer to the question, whether perfect fluid
  is discovered, depends on relatively unknown
  initial conditions.
• Glauber Early thermalization perfect fluid QGP
• CGC No perfect fluid QGP?
• Discovery of EITHER a perfect fluid QGP OR the
  CGC a viscous fluid QGP?

11
How Large Hadronic Rescattering?

• Hybrid Model
• QGP Fluid Hadronic Gas Glauber I.C.
• Hydro Model
• QGP Fluid Hadronic Fluid Glauber I.C.

Comparison?Try to draw information on hadron gas

• Key technique in hydro
• Partial chemical equilibrium in hadron phase
• Particle ratio fixed at Tch
• Chemical equilibrium changes dynamics.
• TH and K.Tsuda(02),TH
  and M.Gyulassy(06)

12
Hydro HydroCascade for Protons

• Tth 100 MeV
• Shape of spectrum
• changes due to
• radial flow rather
• than hadronic
• dissipation for
• protons.

radial flow
13
Opposite Behaviors for Pions
Green line
Teaney(03)
Caveat Transverse expansion Non-scaling solution
Harder Hadronic Gas (Viscous pressure)
Softer Hadronic Fluid (pdV work)
14
Hadronic Dissipation Suppresses Differential
Elliptic Flow
Difference comes from dissipation only in the
hadron phase

• Relevant parameter Gs/t
• Teaney(03)
• Dissipative effect is not so
• large due to small expansion
• rate (1/tau 0.05-0.1 fm-1)

Caveat Chemically frozen hadronic fluid is
essential in differential elliptic flow. (TH and
M.Gyulassy (06))
15
Mass Splitting Comes from the Late Hadronic Stage
Pion Generation of v2 in the hadronic
stage Proton Radial flow effects
Huovinen et al.(01)
Pion
Mass splitting itself is NOT a direct
signature of perfect fluid QGP.
Proton
16
v2(h) fromQGP Hydro Hadronic Cascade
Suppression due to hadronic dissipation
17
Excitation Function of v2

• Hadronic Dissipation
• is huge at SPS.
• still affects v2 at RHIC.
• is almost negligible at LHC.

18
Summary of the 1st Topic

• An answer to the question, whether perfect fluid
  is discovered, depends on relatively unknown
  initial conditions.
• Protons pT slope becomes harder due to radial
  flow.
• Pions pT slope becomes harder due to
  dissipation. However, it becomes softer due to
  pdV work in the case of no viscosity.
• The effect of hadronic dissipation is large in
  small multiplicity as expected.

19
Hadronization through Jet-Fluid Strings
T.Hirano, M.Isse, Y.Nara, A.Ohnishi, K.Yoshino,
(in preparation).
Space-time evolution of the QGP fluid ?Open data
table
Energy loss ? GLV 1st order
String Fragmentation ?PYTHIA (Lund)
In Rudy Hwas language, this model describes
shower-shower, shower-thermal, NOT
thermal-thermal.
20
http//nt1.c.u-tokyo.ac.jp/hirano /parevo/parevo.
html
T.Hirano, talk at Interaction between hard
probes and the bulk (tomorrow)
21
Comparison btw two mechanisms
Lorentz-boosted thermal parton distribution at
TTc hyper surface from hydro simulations
22
pT distributions
GLV 1st order (simplified) formula
20-30 centrality
Effective parton density from hydro
Fitting the pT data is our starting point.
Independent fragmentation C2.5-3.0 Jet-fluid
string C8.0

• Fluctuation of the number of emitted gluon
• Chemical non-equilibrium in the QGP phase
• Higher order in opacity expansion
• Cronin effect

Neglecting many effects
23
v2 _at_ intermediate-high pT
p
20-30 centrality
v2(JFS) 0.1 at b8 fm without assuming an
unrealistic hard sphere
24
High pT v2 puzzle!?
STAR, PRL93,252301(04)
25
Mechanism 1
Additional push!
In order to compensate this effect, one needs
additional parton energy loss in comparison with
independent fragmentation scheme. This enhances
v2.
26
Mechanism 2
Direction of jets Radial on average
Direction of string momentum is tilted to
reaction plane in comparison with collinear
direction.
Direction of flow Perpendicular to surface
27
Summary of the 2nd topic

• Hadronization through jet-fluid strings
• Realistic space-time evolution of thermalized
  partons is considered through hydrodynamic
  simulations. (Data table is now available on the
  web!)
• v2 is enhanced in intermediate-high pT regions.

28
Source Function from 3D Hydro Cascade
How much the source function differs from ideal
hydro in Configuration space?
Blink Ideal Hydro, Kolb and Heinz (2003) Caveat
No resonance decays in ideal hydro