Transcript PowerPoint Presentation - J/

Search for Partonic EoS in
High-Energy Nuclear Collisions
Nu Xu
Lawrence Berkeley National Laboratory
Many thanks to the conference organizers
and
S. Blyth, S. Esumi, H. Huang, Y. Lu, M. Oldenburg, H. Ritter, K. Schweda, P. Sorensen, Z. Xu, Yifei Zhang
M. Bleicher, P. Houvinen, V. Koch, K. Redlich, ….
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
1/20
Outline
 Motivation
- s-quark and c-quark are special
- equation of state
- collectivity, local thermalization
 Particle spectra and v2
- partonic collectivity from multi-strange hadrons
- hint of charm collectivity
 Summary and outlook
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
2/20
QCD Energy Scale
ms ~ 0.2 GeV, similar to values
TC
QCD
TCH
critical temperature
QCD scale parameter
chemical freeze-out temperature
 = 4f scale for  symmetry breaking
u-, d-, s-quarks: light-flavors
Strange-quark hadronization
Nu Xu
mc ~ 1.2 - 1.5 GeV >> QCD
- pQCD production - parton density at small-x
- QCD interaction - medium properties
Rcc ~ 1/mC => color screening
J/ => deconfinement and thermalization
c-, b-quarks: heavy-flavors
Charm-quark thermalization
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
3/20
Equation of State
 T   0
 j   0
j  (x)  n(x)u  (x)
T   (x)  p(x)u  u  g   p(x)
Energy density  GeV/fm3
EOS - the system
response to the changes
of the thermal conditions is fixed by its p and T ().
Equation of state:
- EOS I : relativistic ideal gas: p = /3
- EOS H: resonance gas: p ~ /6
- EOS Q: Maxwell construction:
Tcrit= 165 MeV, B1/4 = 0.23 GeV
lat=1.15 GeV/fm3
P. Kolb et al., Phys. Rev. C62, 054909 (2000).
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
4/20
Physics Goals at RHIC
Identify and study the properties of
matter with partonic degrees of
freedom.
Penetrating probes
Bulk probes
- direct photons, leptons
- “jets” and heavy flavor
- spectra, v1, v2 …
=
- partonic collectivity
- fluctuations

jets
- observed high pT hadrons (at RHIC, pT(min) > 3 GeV/c)
Hydrodynamic
Local
Collectivity
collectivity
- collective motion of observed hadrons, not necessarily
reached
Flow
Thermalization
thermalization among them.
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
5/20
High-energy nuclear collisions
Initial Condition
- initial scatterings
- baryon transfer
- ET production
- parton dof
Q2
Nu Xu
J/,D
partonic scatterings,
early thermalization?
TC
Tch
W
f
elliptic flow v2
X
System Evolves
- parton interaction
- parton/hadron
expansion
Bulk Freeze-out
- hadron dof
- interactions stop
jets

,K, K*
D,p
time
d, HBT
radial flow bT
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
Tfo
6/20
Hadron spectra from RHIC
p+p and Au+Au collisions at 200 GeV
Multi-strange hadron spectra are exponential in their
shapes.
STAR white papers - Nucl. Phys. A757, 102(2005).
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
7/20
Yields ratio results
data
Thermal
model fits
Tch = 163 ± 4 MeV
B = 24 ± 4 MeV
- In central collisions, thermal model fit well with S = 1. The system is
thermalized at RHIC.
- Short-lived resonances show deviations. There is life after chemical
freeze-out.
RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184.
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
8/20
Blast wave fits: Tfo vs. < bT >
200GeV Au + Au collisions
1) , K, and p change
smoothly from peripheral
to central collisions.
2) At the most central
collisions, bT reaches
0.6c.
3) Multi-strange particles f,
W are found at higher T
and lower bT
 Sensitive to early
partonic stage!
 How about v2?
Multi-strange hadrons freeze-out with
higher Tfo (~Tch) and smaller bT
Nu Xu
STAR: NPA715, 458c(03); PRL 92,
112301(04); 92, 182301(04).
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
9/20
Compare with hydro-model results
The model results fit to pion, Kaon, and proton spectra well, but over predicted
the values of <pT> for multi-strange hadrons. Multi-strange hadrons freeze-out
earlier!
P. Kolb and R. Rapp, Phys. Rev. C62, 054909 (2000).
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
10/20
T vs. mass plot (SPS)
H. van Hecke, H. Sorge, N. Xu, Phys. Rev. Lett. 81, 5764(98).
Interactions with hadronic gas:
 Large x-section limit:
pions, kaons, protons
Tfo  Tthermal  C  mass  b 2
 Small x-section limit:
W, J/

mi2  pt2 
 i  exp- 




sensitive to hadronization!
At SPS, the observed collective transverse flow, b~ 0.4c,
develops mostly at the hadronic stage. W and J/ do not flow!
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
11/20
Slope parameter systematics
sps
At RHIC, f, X, W, and J/ show collective motion in
200 GeV Au + Au central collisions!
PHENIX (, K, p, J/): PRC69, 034909(04), QM05; STAR (f, X, W): QM05.
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
12/20
Anisotropy parameter v2
coordinate-space-anisotropy

momentum-space-anisotropy
y
x
 y2  x2
 2
 y  x2
py
v 2  cos2 ,   tan ( )
px
1
Initial/final conditions, EoS, degrees of freedom

Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
13/20
v2 of multi-strange hadrons
‘Strangeness’ flows - partonic collectivity at RHIC!
* Inconsistencies in current hydro calculations
STAR Preliminary, QM05 conference
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
14/20
Collectivity, Deconfinement at RHIC
- v2, spectra of light hadrons
and multi-strange hadrons
- scaling of the number of
constituent quarks
At RHIC, I believe we have
achieved:
 Partonic Collectivity
 Deconfinement
PHENIX: PRL91, 182301(03)
STAR: PRL92, 052302(04), 95, 122301(05)
nucl-ex/0405022
S. Voloshin, NPA715, 379(03)
R.J. Fries et al., PRC69, 031902(03)
Models: Greco et al, PRC68, 034904(03)
X. Dong, et al., Phys. Lett. B597, 328(04).
….
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
15/20
Dynamic model results
Models seem to work in
2.5 <pT<5 GeV/c
In those models, almost
no interactions at the late
hadronic stage. Flow has
developed prior to
hadronization:
 partonic collectivity
 deconfinement
* No collective flow in reco calculations
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
16/20
However, hadronic transport …
RQMD results show the particle
type dependence although the
absolute amplitudes of v2 are a
factor of 2 or so too small!
1) At low pT region: mass
ordering - feature of
hydrodynamic motion
2) Hadron type dependence at
the intermediate pT region vacuum hadronic cross sections
used in the model.
Y. Lu et al., nucl-th/0602009
NCQ-scaling is unique, but the explanation may be not!
* Reco versus transport mode calculations.
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
17/20
f -mesons flow = partonic flow
f-mesons are very special:
- they do not re-interact in hadronic environment
- they are formed via coalescence with thermal s-quarks
- they show strong collective flow
STAR Preliminary: QM05, M. Lemont, S. Blyth talks
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
18/20
Multi-strange hadron ratios
STAR Preliminary
STAR Preliminary
In heavy ion collisions at RHIC, up to pT ~ 4 GeV/c, (*model predicts 8
GeV/c) the strangeness production is dominated by the thermal like
processes.
*Hwa and Yang, nucl-th/0602024; STAR data: QM05, S. Blyth talk
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
19/20
Summary and outlook
Experimental results from RHIC:
 Jet-quenching - hot and dense matter
 Strong collective flow -Interacting matter
 Chemical freeze-out near the phase boundary
 f (ss), W (sss), J/ (cc) show partonic collectivity
at RHIC
(at SPS: f, W, J/ v2 should be close to zero)
Next Step:
 Measure the partonic velocity to infer pressure parameter - important
for mapping the EoS at RHIC.
 In order to further demonstrate the early partonic thermalization, one
needs to measure the heavy-flavor collectivity = light-flavor
thermalization - RHIC heavy-flavor program, LHC.
 In order to demonstrate the phase transition in high-energy nuclear
collisions, one needs to identify the critical point - RHIC low energy
scan and GSI CBM experiments.
Nu Xu
International Conference on Strangeness in Quark Matter, UCLA, March 26 - 31, 2006
20/20