Download What can we learn from hydrodynamic analysis at RHIC?

Workshop on Quark-Gluon-Plasma Thermalization
August 10-12, TU Wien, Vienna, Austria
What can we learn from hydrodynamic
analysis
at RHIC?
Tetsufumi Hirano
Dept. of Physics, Columbia Univ.
T.H. and M.Gyulassy, nucl-th/0506049
T.H., Y.Nara et al., in preparation.
Outline
1. Perfect fluidity of sQGP core and highly
dissipative hadronic corona
2. CGC + full 3D hydro + cascade
3. Hydrodynamic analysis suggests even a
signal of
DECONFINEMENT?!
Basis of the Announcement
Our claims:
PHENIX white paper
NA49(’03)
1. Ideal hydrodynamics
accidentally reproduces these
data!
2. Nevertheless, “perfect fluidity of
the sQGP” statement still holds.
Integrated elliptic flow
WHY!!!???
Differential elliptic flow
Common initial time in hydro ~ 0.6-1.0 fm/c
A big surprise!
Classification of Hydro Models
Tc
QGP phase
T
Model CE:
Kolb, Huovinen
Heinz, Hirano…
Model PCE:
Hirano, Teaney;
Kolb…
Model HC:
Teaney, Shuryak,
Bass, Dumitru,
Nonaka…
~1 fm/c
Perfect Fluid of QGP
~3 fm/c
Chemical
Equilibrium
EOS
Tth
Tch Partial
Chemical
Equilibrium
EOS
Tth
ideal hydrodynamics
Hadronic
Cascade
~10-15
fm/c
t
Are hydro results consistent?
If not, what does it mean?
p
PartialCE
elliptic flow
HadronicCascade
Chem.Eq.
pT spectra
PHENIX white paper, NPA757,184(2005)
p
Kolb and Heinz(’04)
Differential Elliptic Flow Develops
in the Hadron Phase?
Is v2(pT) really sensitive
to the late dynamics?
140MeV
0
0.2
0.4
0.2 0.4 0.6
0
0.6 0.8
transverse momentum (GeV/c)
0.8
1.0
T.H. and K.Tsuda (’02)
100MeV
Mean pT is the Key
Generic
feature!
t
Slope of v2(pT) ~ v2/<pT>
t
Response to decreasing Tth
(or increasing t)
v2
CE
t
PCE
<pT>
v2/<pT>
v2(pT)
At hadronization
Chemical Eq.
v2
v2
freezeout
<pT>
pT
v2(pT)
<pT>
pT
Chemical F.O.
v2
v2(pT)
Accidental Reproduction of
v2(pT)
<p >
p
PHENIX white paper, NPA757,184(2005)
1.Why mean pT behaves so differently?
2. Why CE result ~ HC result?
PartialCE
HadronicCascade
Chem.Eq.
For a more rigorous discussion, see T.H. and M.Gyulassy, nucl-th/0506049
Intuitive Picture
Chemical
Freezeout
Mean ET
decreases
due to pdV
work
ET per particle increases
in chemical equilibrium.
This effect delays cooling of the system like a
viscous fluid.
 Chemical equilibrium
MASS energy
imitates viscosity
Chemical
at the cost of particle yield!!!
Equilibrium
KINETIC
energy
Chem. Eq. Imitates Viscosity!
Contour(T=const.)
T(t) at origin
T.H. and K.Tsuda(’02)
Model CE
<vr>(Tth)
t
Model PCE
Summary of Hydro Results
Models for
Hadron
Phase
Chemical
Equilibrium
Partial
Chemical
Equilibrium
Hadronic
Cascade
v2(pT,m)
pT
spectra
Yield
or ratio
Viscous
effect
Caveat
Y“No-Go
es
Yes* Ntheorem”
o
No
* P (Pbar) yields
<< exp. data
No
Yes
YRuled
es*
Yes
Yes
N
out!
*Only low pT for
pions
o
Yes Yes*
*Kinetic approach
•Boundary
(QGPhadron)
WINNER for hydro race at RHIC !
Hybrid model (Ideal QGP fluid + dissipative hadron gas)
by Teaney, Lauret, and Shuryak
The End of 50-Year-Old
Ideal, Chem. Eq. Hadronic Fluid
After the famous Landau’s paper (1953),
ideal and chemical equilibrium hadronic
hydrodynamics has been exploited for a
long time. However, the model may not
be used when chemical freezeout
happens earlier than thermal freezeout
since it accidentally reproduces
pT spectra and v2(pT)
at the cost of particle yields in a way that
it imitates viscosity.
Digression
A Long Long Time Ago…
…we obtain the value R (Reynolds number)=1~10…
Thus we may infer that the assumption of the
perfect fluid is not so good as supposed by Landau.
Summary 1
Critical data harvested at RHIC
1.Particle ratio (Particle yield)
2.pT spectra
3.v2 AND v2(pT)
Hydrodynamic analyses
Nearly perfect fluidity of the sQGP core
AND
Highly dissipative hadronic corona
Part 2
Results from CGC + full 3D
hydro + hadronic cascade
T.H. and Y.Nara, PRC66(’02)041901, 68(’03)064902, 69(’04)034908, PRL91(’03)082301, NPA743(’04)305
CGC
(a la KLN)
(MV model
on 2D lattice)
Collinear factorized
Color Quantum
Fluid(QS2<kT2<QS4/L2) Parton distribution
(x-evolution eq.)
LOpQCD
(kT factorization)
(classical Yang-Mills
on 2D lattice)
(full 3D hydro)
Hadronic
cascade
(PYTHIA)
Jet quenching
Parton energy loss
(a la Gyulassy-Levai-Vitev)
Recombination
Fragmentation
(JAM)
Low pT
(CTEQ)
Transverse momentum
Shattering CGC
Hydrodynamics
Proper time
Hadron QGP
gas
Parton
production
(dissipative
process?)
Nuclear wave
function
Parton
distribution
Toward a Unified Model in H.I.C.
Intermediate pT
High pT
CGC + Full 3D Hydro + Cascade
t
Hadronic
Corona
(Cascade,
JAM)
z
0
c.f. Recent similar approach by Nonaka and Bass (DNP04,QM05)
sQGP core
(Full 3D
Hydro)
Color
Glass
Condensate
v2(h) from CGC + Full 3D Hydro
+ Hadronic Cascade
PHOBOS data:
“Triangle shape”
prop. to dN/dh
Tth=100MeV:
“Trapezoidal shape”
Typical hydro result
Tth=169MeV:
Triangle shape!
Just after hadronization
CGC+hydro+cascade:
Good agreement!
Perfect fluid sQGP core +
dissipative hadronic corona
picture works in forward region!
CGC+Hydro+Cascade
in Cu+Cu Collisions
The effect of rescattering
is seen especially
near midrapidity.
Predictions for LHC
from CGC+Hydro+Cascade
•No jet components
•Need to estimate
systematic error from
Cooper-Frye formula
•Monotonic increase is
consistent with previous
work by Teaney et al.
Early Thermalization in Peripheral
Collisions at RHIC?
•CGC + hydro + cascade
agreement only up to
15~20% centrality
(impact parameter ~5fm)
•Centrality dependence
of thermalization time?
Common t0=0.6fm/c
Semi-central to peripheral collisions:
Not interpreted only by hadronic dissipation
Important to understand pre-thermalization stage
Imcomplete thermalization? (Talk by Borghini)
Part 3
Does the hydrodynamic
hydro+cascade
agreement with experimental
data suggest even
DECONFINEMENT?!
Viscosity and Entropy
•Reynolds number
Iso, Mori, Namiki (1959)
R>>1
Perfect fluid
where
•1+1D Bjorken flow
(Ideal)
h : shear viscosity (MeV/fm2)
s : entropy density (1/fm3)
h/s is a good dimensionless measure
to see viscous effects.
(Viscous)
T.H. and M.Gyulassy (’05)
What Have We Learned?
h : shear viscosity, s : entropy density
•Absolute value of viscosity
•Its ratio to entropy density
!
What makes this sudden behavior?
Summary
• The sQGP core + the dissipative hadronic corona
picture can be established through careful
comparison of current hydro results with high
precision RHIC data.
• This picture is confirmed in forward rapidity
region by using a “cutting edge” hybrid model (CGC
+ full 3D hydro + hadronic cascade).
• This picture is manifestation of the sudden
change of entropy density at Tc, namely
deconfinement!