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Dynamical Modeling of Relativistic Heavy Ion Collisions. Tetsufumi Hirano. Work in partly collaboration with Y.Nara (Frankfurt), M.Gyulassy (Columbia). Workshop at RCNP, Nov 4, 2004. The Five Pillars of RHIC Wisdom. Slide from T.Hallman Talk@ICHEP04 ~STAR white paper. Ideal hydro. - PowerPoint PPT Presentation
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Dynamical Modeling of Dynamical Modeling of Relativistic Heavy Ion Relativistic Heavy Ion
CollisionsCollisionsTetsufumi Hirano
Workshop at RCNP, Nov 4, 2004
Work in partly collaboration withY.Nara (Frankfurt), M.Gyulassy (Columbia)
…suggest appealing QGP-based picture of RHIC collision evolu-tion, BUT invoke 5 distinct models, each with own ambigu-ities, to get there. pQCD parton E loss
The Five Pillars of RHIC WisdomThe Five Pillars of RHIC WisdomIdeal hydro
Quark recombination constituent q d.o.f.
CGC
Statistical model
Early thermalization + soft EOS
Very high inferred initial gluon density
Very high anticipated initial gluon density
u, d, s equil-ibration near Tcrit
Slide from T.HallmanTalk@ICHEP04~STAR white paper
The State of RHIC TheoryThe State of RHIC Theory
LQCD: CPU limitations; applic’y to dynamic matter?
Statisticalmodel:
equilib’n or phase space?
Hydro: 0, freezeout,
boost-invariance
ambigs.
Quark recomb.: predictive
power?Parton E loss:
untested assump-
tions
Gluon saturation: universal
scale estab-lished?
Emerging description of beautiful evolution from one
new state of matter to another!
AndYet,
A patchwork, with model parameters adjusted independ-
ently for each element
In order to rely on theory for compelling QGP discovery claim, we need: greater coherence; fewer adjusted parameters; quantitative
estimates of theoretical uncertainties
Slide from T.HallmanTalk@ICHEP04~STAR white paper
Hairsplitting Comments from Our Approach
How are these consistent with each other?
Discussion from hydrodynamic point of view:1. Hydro vs. Statistical model (main topic)2. Hydro vs. Recombination model3. Hydro vs. Jet tomography4. Hydro vs. CGC
These discussions will tell us what to do nextand lead to a unified understanding of HIC.
Today’s Bad NewsToday’s Bad News
The elliptic flow at RHIC is
“accidentally”reproduced by a hydro model.
Hydro vs. Statistical Model (1)
Chemical parameters particle ratioThermal parameters pt spectra
•Statistical modelTch>Tth
•(conventional) hydroTch=Tth
• No reproductionof ratio and spectrasimultaneously
Hydro vs. Statistical Model (2)
P.Huovinen, QM2002 proceedings
Hydro vs. Statistical Model (3)
iIntroduction of chemical potentialfor each hadron!
•Single Tf in hydro•Hydro works?•Both ratio andspectra?
Hydro vs. Statistical Model (4)
EOS
Example of chem. potential
Partial chemical equilibrium (PCE)
Expansion dynamics is changed(or not)?
T.H
. an
d K
.Tsu
da(
’02)
Hydro vs. Statistical Model (5)
Model PCE
Model CE
Contour(T=const.)
T() at origin
T.H
. an
d K
.Tsu
da(
’02)
<vr>(Tth)
Hydro vs. Statistical Model (6)
•How to fix Tth in conventional hydro• Response to pT slope• Spectrum harder as decrease Tth
• Up to how large pT?
•Tth independence of slope in chemicallyfrozen hydro
• No way to fix Tth
• Suggests necessity of (semi)hard components
Charged hadronsin AuAu 130GeV
Hydro vs. Statistical Model (7)
ChemicalEquilibrium
PartialChemical
Equilibrium
K
p
T.H. and K.Tsuda (’02)
Ko
lb a
nd
Hei
nz(
’04)
Is v2(pT) sensitive to the late dynamics?
Hydro vs. Statistical Model (8)
Slope of v2(pT) ~ v2/<pT> Response to decreasing Tth
(or increasing )v2 <pT> v2/<pT>
CE
PCE
Genericfeature!
pdV work + (number)/(entropy)
Hydro vs. Statistical Model (9) Simplest case: Pion gas
Longitudinal expansion pdV work!
dET/dy should decrease with decreasing Tth. <ET>dN/dy should so.
CFO: dS/dy = const. dN/dy = const. <pT> decreases
CE: dS/dy = const.dN/dy decreases (mass effect)<pT> can increase as long as <ET>dN/dy decreases.
Hydro vs. Statistical Model (10)
PHENIX white paper, nucl-ex/0410003
Hydro vs. Statistical Model (11)
•Choice of Tth in conventional hydro results fromneglecting chemical f.o.•The great cost one has to pay for “simplification”!• Importance of chemical potential for each hadronswithin hydrodynamics• “No-Go theorem”. Yet you use?• >90% hydro results at SPS and RHIC do not make sense!•Chemical eq. mimics viscous hydro?
Today’s Good NewsToday’s Good NewsCurrently,
hydro+cascade is the only modelwhich reproduces
the elliptic flow, particle ratio, andparticle spectra.
Caveat: Need realistic interface andoversampling to get rid of numericalartifacts.
D.Teaney et al., nucl-th/0110037.
Hydro vs. Recombination (1)
R.J
.Fri
es
et a
l. (’
03)
Tc=175MeV & vT = 0.55???
reco(Duke)
T.H
. and K.T
suda (’02)
Half of radial flow comes from hadron phase in hydro
Parameter dependence?
Today, I won’t discuss (violation of) energy conservation,decrease of entropy…
Hydro vs. Recombination (2) Soft+hard reco is
important?Naïve idea:Hydro+jet modelwith recombinationvia string fragmentation
PHENIX “modelkiller” plot!nucl-ex/0408007 Pick
up apartonfromQGP
Only mass effect
T.H
.,QM
200
4
Associated yield1.7<pT<2.5GeV/c
Hydro vs. Jet Tomography (1)
I.Vite
v, n
ucl
-th
/04
040
52
Input: RAA
Output:
T.H
. an
d Y.N
ara (’0
4)
Input: dNch/dOutput:
consistent?
Hydro vs. Jet Tomography (2)Jet tomography:
“Color charge density”Hydrodynamics:Parton density
cf.) Parton density in chem. eq.
Not complete chem. eq.! Need chemical non-eq. description
rate eq. for ng and nq
(Nf=3), (Nf=2)
>
<
Hydro vs. CGC (1)K
har
zeev
an
d L
evi
n (
’01
)
Gluons produced fromtwo CGC collisions (KLN)
ET/N ~ 1.6 GeVConsistent with classical Yang Mills on 2D lattice (KNV, Lappi)Inconsistent with exp. data ~0.6GeV
T.H
. an
d Y.N
ara(’0
4)
Hydro vs. CGC (2)Gluons produced fromtwo CGC collisions (KLN)
ET/N ~ 1.6 GeV
Initial conditionof hydrodynamicsimulations
ET/N ~ 1.0 GeV ET/N ~ 0.55 GeV Consistent withclassical Yang Millson 2D lattice (KNV)
Consistent withexp. data ~0.6 GeV
Final (psuedo)rapidityspectra of all hadrons
This should be obtained through non-equilibrium processes.
Production of entropy
Hydrodynamic evolution“PdV work” reduces ET/N.
Hydro vs. CGC (3)•Need a mechanism to reduce ET/N ?•ET and/or N •Non-equilibrium description is extremely important.
•Can we get a short thermalization time (~1fm/c)?•Is Boltzmann (elastic+inelastic) sufficient for this?•If not, may we need non-eq. quantum field approaches?
Summary so far
We should keep in mind in modeling of HIC:1.“The right model in the right place” basis
• Time scale• Energy/momentum scale
2.Consistency among models3.Treatment of interface among models4.The number of parameters/assumptions as small as possible