1. Search for Quark-Gluon Plasma at RHIC
Byungsik Hong
Korea University

2. Relativistic Heavy-Ion Collisions
Approaching
v > 0.9c
Collisions
Passing
through
Expansion
Some of beam energy they had before is transformed into heat and new particles right here !
May 6, 2004
Hanyang University

3. Nuclear Phase Diagram T(MeV) Density(n0) Early Universe (RHIC) ~150
~10
Early Universe
(RHIC)
Color Superconductor
Neutron Star
Hadron Gas
Quark-Gluon Plasma
Phase Transition
Atomic Nuclei
RHIC & future LHC explore high temperature & low baryon density partonic matter.
SIS explores high baryon density hadronic matter.
May 6, 2004
Hanyang University

4. Relativistic Heavy-Ion Accelerators
c.m. Energy
(GeV)
Status
SIS18
(GSI, Germany) 2A
(A=mass number)
Running
AGS
(BNL, USA) 5A
Finished
SPS
(CERN, Switzerland)
20A
Finish soon
RHIC
200A
Running since 2000
SIS300
(GSI, Germany) 8A
Just approved; Plan to run from ~2010
LHC
(CERN, Switzerland)
5500A
Plan to run from ~2007
May 6, 2004
Hanyang University

5. Relativistic Heavy Ion Collider
Brookhaven National Lab.
in New York
Circumference: 3.83 km
First collision: 2000
100A GeV Au+Au(2X1026/cm2/s)
250 GeV p + p (2X1032/cm2/s)
PHENIX
STAR
May 6, 2004
Hanyang University

6. More about the PHENIX PHENIX= Pioneering High Energy
Nuclear Interaction eXperiment
May 6, 2004
Hanyang University

7. The STAR Detector STAR=Solenoid Tracker at RHIC Magnet
Coils
Central
Trigger
Barrel
(CTB)
ZCal
Time
Projection
Chamber
(TPC)
Year 2000
Barrel EM Cal (BEMC)
Silicon Vertex Tracker (SVT) Silicon Strip Detector (SSD) mVertex Detector
FTPC Endcap EM Cal FPD
TOFp, TOFr Year 2001/2003
Year 2006+
May 6, 2004
Hanyang University

8. Outline Collective flow HBT High pt hadron suppression Jet quenching
Summary of the Quark Matter 04 Conference
3D imaging of the hot fireball
See more deep inside
May 6, 2004
Hanyang University

9. Collective Flow
Reaction plane
time
reaction plane
transverse plane
(at midrapidity)
v2< v2 >0
elliptic flow
RN=(1+ v2)/(1-v2)
v1<0 v1 >0
sideward flow
px = v1 pt
Fourier expansion of azimuthal distribution gives the phase space distribution w.r.t. the reaction plane.
S. Voloshin & Y. Zhang, Z. Phys. C70, 665 (1996)
J.Y. Ollitrault, Nucl. Phys. A638, 195c (1998)
May 6, 2004
Hanyang University

10. Anisotropic Flow v1, v2, v4, … h~-3 h~3 h~0 v2 = 15% v2 = 15%, v4=4%
η∼-3
η∼0
η∼3
Anisotropic Flow v1, v2, v4, … x z
h~-3
h~3
h~0
Reaction
plane
Spectators
Spectators
1.5
v2 = 15%
v2 = 15%, v4=4% Y 1
Out-of-plane
0.5
In-plane X
v2 = 7%
v2 = 7%, v1=+7%
v2 = 7%
v2 = 7%, v1=-7%
May 6, 2004
Hanyang University
Isotropic emission

11. Poster by Hiroshi Masui
Directed Flow v1
STAR, PRL92, (2004)
NA49, PRC69, (2003)
M. Belt-Tonjes for PHOBOS (QM04)
H. Masui for PHENIX (QM04)
Consistent among RHIC Expts.
Shape in forward rapidity agree with low energy data by NA49
Elongated shape near midrapidity
May 6, 2004
Hanyang University
PHENIX preliminary
Poster by Hiroshi Masui

12. v2 vs Rapidity v2 is positive: v1 and v2 are in the same plane STAR
M.B. Tonjes for PHOBOS (QM04)
v2 is positive:
v1 and v2 are in the same plane
May 6, 2004
Hanyang University

13. v2 vs pt including strangeness
Scaled with the number
of quarks except π±
This saturation can be explained by the surface emission due to the dense & opaque medium,
Shuryak, PRC 66, (2002)
STAR Preliminary
Quark coalescence at RHIC?
D. Molnar and S.A. Voloshin, PRL 91, (2003)
Critical test by pentaquark with n=5
May 6, 2004
STAR, PRL92, (2004)
Hanyang University

14. HBT interferometry Final-state effects (Coulomb, strong) also need
Two-particle interferometry: p-space separation  space-time separation
qout
qside
qlong
Rside
Rlong
Rout p1 p2 x1 x2
q (GeV/c)
C (q) 1 2
Final-state effects (Coulomb, strong) also need
to be accounted for.
Gaussian model (3-d):
May 6, 2004
Hanyang University

15. HBT Excitation Function of π
STAR, PRL 87, (2001)
kT-dependence
Agree among RHIC expts.
May 6, 2004
Hanyang University

16. Azimuthally Sensitive π HBT
Probes spatial anisotropy at freeze-out Wiedemann, PRC57, 266 (1998)
Freeze-out shape probes nature & timescale of system evolution
How much initial spatial deformation survives system expansion?
late rescattering
hydrodynamic expansion
time
beam into screen
Initial geometry → aniosotropies in pressure gradients  
Preferential in-plane expansion → decreases spatial anisotropy 
Freeze-out source shape →
model dependent measure of pressure, expansion time
May 6, 2004
Hanyang University

17. Azimuthally sensitive π HBT
reaction plane
qout
qside
qlong 
Rside2
 = 90°
Rside (small)
Rside (large)
 = 0°
May 6, 2004
Hanyang University

18. HBT(): Centrality & kT dependence
Au+Au, √s = 200 GeV
STAR, nucl-ex/
May 6, 2004
Hanyang University

19. System deformation at Freeze-out
Final state eccentricity from v2
HBT with respect to the reaction plane b t
May 6, 2004
Hanyang University

20. Nuclear Modifications to Hard Scattering
PHENIX, PRL91, (2003); 88, (2002) q
Large Cronin effect at low energy
Large suppression at RHIC (jet quenching)
Is the suppression due to the medium (Initial or final state effect)?
May 6, 2004
Hanyang University

21. d+Au Control Experiment
Nucleus
-nucleus
collision
Proton/deuteron VS
Collisions of small with large nuclei were always foreseen as necessary to quantify cold nuclear matter effects.
Recent theoretical work on the “Color Glass Condensate” model provides alternative explanation of data:
Jets are not quenched, but are a priori made in fewer numbers.
Kharzeev, Levin, & Nardi, NPA730, 448 (2004)
Small + Large distinguishes all initial and final state effects.
May 6, 2004
Hanyang University

22. RAA vs RdA for Identified p0
d+Au
Au+Au
Initial State Effects Only
Initial + Final State Effects
d-Au results rule out CGC as the explanation for jet suppression at central rapidity and high pT
May 6, 2004
Hanyang University

23. Charged Hadron Results
Striking difference of d+Au and Au+Au results.
Charged Hadrons higher than neutral pions.
Cronin Effect:
Multiple Collisions broaden high PT spectrum
May 6, 2004
Hanyang University

24. Centrality Dependence
Au + Au Experiment
d + Au Control Experiment
PHENIX, PRL91, (2003)
Final Data
Preliminary Data
Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control one.
Jet Suppression is clearly a final state effect.
May 6, 2004
Hanyang University

25. Rcp Variable Rcp=binary-collision scaled centrality ratio
STAR, PRL92, (2004)
Rcp=binary-collision scaled centrality ratio
This suppression can be explained by the parton energy loss due to the dense & opaque medium,
Gyulassy & Wang, NPB 420, 583 (1994)
Mesons and baryons show different behaviors.
 Dependence on the number of valence quarks
 Support the quark coalescence again
May 6, 2004
Hanyang University

26. Jet Quenching; Azimuthal dependence
2-Particle Correlations: dN/d()
trigger
“Trigger”  = 0
near-side
away-side
STAR, PRL90, (2003)
May 6, 2004
Hanyang University

27. Disappearance of the Away-Side Jet
di-hadron
1/NtriggerdN/d()
STAR, PRL91, (2003); 90, (2003)
Background subtracted
Near side jet “identical”
ppdAuAuAu
p+p: 2 jets
d+Au: 2 jets
Au+Au peripheral
2 jets
Au+Au central
1 jet !
May 6, 2004
Hanyang University

28. Path Length Dependence
di-hadron, % central
STAR Preliminary
In-plane
Out-of-plane
Measured
Reflected
Suppression is larger in out-of-plane (longer path length) !
May 6, 2004
Hanyang University

29. Path Length Dependence
di-hadron, % Central
Out-of-plane
In-plane
Jet quenching is consistent with path length dependence !
May 6, 2004
Hanyang University

30. Particle Dependence of Asymmetry
Associated
Mesons
PHENIX Preliminary
Associated
Baryons
Noticeable differences in the asymmetries for
associated baryons and mesons
May 6, 2004
Hanyang University

31. Conclusions Flow HBT Jet Quenching
A wealth of hadron data becomes available for v1, v2 (even v4 and v6 from STAR).
Electron and charm flows from PHENIX
HBT
Out-of-plane extended source at freeze-out
Short lived system remembers its initial spatial geometry
Jet Quenching
Cronin in d+Au
Suppression/non-suppression follow baryon/meson line (not mass): more suppression for mesons.
Away-side jet quenching in central Au+Au
Azimuthal dependence consistent with the path length dependence by HBT
May 6, 2004
Hanyang University