Transcript Search for Quark-Gluon Plasma at RHIC

Search for
Quark-Gluon Plasma at RHIC
Byungsik Hong
Korea University
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
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Nuclear Phase Diagram
Early Universe
(RHIC)
T(MeV)
RHIC & future
LHC
~150
explore high
temperature & low
baryon density
partonic matter.
Quark-Gluon Plasma
Phase Transition
Hadron Gas
Color Superconductor
Neutron Star
SIS explores high
Atomic Nuclei
baryon density~10
hadronic matter.
May 6, 2004
Hanyang University
Density(n0)
3
Relativistic Heavy-Ion Accelerators
Accelerator
c.m. Energy
(GeV)
Status
SIS18
(GSI, Germany)
2A
(A=mass number)
Running
AGS
(BNL, USA)
5A
Finished
SIS300
(GSI, Germany)
8A
Just approved; Plan
to run from ~2010
SPS
(CERN, Switzerland)
20A
Finish soon
RHIC
(BNL, USA)
200A
Running since 2000
LHC
(CERN, Switzerland)
5500A
Plan to run from
~2007
May 6, 2004
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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)
May 6, 2004
Hanyang University
PHENI
X
STAR
5
More about the PHENIX
May 6, 2004
PHENIX= Pioneering High Energy
6
Nuclear Interaction eXperiment
Hanyang University
The STAR Detector
STAR=Solenoid Tracker at RHIC
Magnet
Barrel EM Cal
(BEMC)
Coils
Silicon Vertex
Tracker (SVT)
Silicon Strip
Detector (SSD)
mVertex Detector
Central
Trigger
Barrel
(CTB)
ZCal
FTPC
Endcap EM Cal
FPD
Time
Projection
Chamber
(TPC)
TOFp, TOFr
Year 2001/2003
Year 2006+
Year 2000
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Outline
1. Collective flow
3D imaging of the hot fireball
2. HBT
3. High pt hadron suppression
 Jet quenching

See more deep inside
Summary of the Quark Matter 04 Conference
May 6, 2004
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Collective Flow
Reaction plane
reaction plane
transverse plane
(at midrapidity)
v1<0
v1 >0
sideward flow
v2<0
v2 >0
elliptic flow
z
y
x
Fourier expansion of azimuthal
distribution gives the phase
space distribution w.r.t. the
reaction plane.
  meas  R
d 3N
 (1  2v1 cos( )  2v 2 cos(2 )  ...)
pt dpt dyd
S. Voloshin & Y. Zhang, Z. Phys. C70, 665 (1996)
px
May 6,Nucl.
2004Phys. A638, 195c (1998)
Hanyang University
J.Y. Ollitrault,
= v1 pt
RN=(1+ v2)/(1-v92)
x
Anisotropic Flow
v1, v2, v4, …
η∼0
η∼-3
η∼3
h~3
h~0
Spectators
Spectators
h~-3
z
1.5
1
v2 = 15%
v2 = 15%, v4=4%
0.5
Out-of-plane
Reaction
plane
Y
In-plane
X
v2 =May
7%
6, 2004
v2 = 7%, v1=+7%
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Isotropic emission
v2 = 7%
v2 = 7%, v1=-7%
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Directed Flow v1
STAR, PRL92, 062301 (2004)
NA49, PRC69, 034903 (2003)
M. Belt-Tonjes for PHOBOS (QM04)
H. Masui for PHENIX (QM04)
May 6, 2004
1. Consistent among RHIC Expts.
2. Shape in forward rapidity agree with
low energy data by NA49
3. Elongated shape near midrapidity
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v2 vs Rapidity
STAR
M.B. Tonjes for PHOBOS (QM04)
v2 is positive:
v1 and v2 are in the same plane
May 6, 2004
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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, 027902 (2002)
Quark coalescence at RHIC?
D. Molnar and S.A. Voloshin, PRL 91, 092301(2003)
Critical test by pentaquark with n=5
May 6, 2004
Hanyang (2004)
University
STAR, PRL92, 052302
STAR Preliminary
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HBT interferometry
• Two-particle interferometry: p-space separation  space-time separation
p1
x1

q
qside
Rside
x2
p2
qout
  
q  p2  p1
 1  
k  p 2  p1 
2
qlong
Rout
Final-state effects (Coulomb, strong) also need
Mayto
6, 2004
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be accounted for.
C (q)
P( p1 , p2 )
real event pairs
C ( p1 , p2 ) 

P( p1 )P( p2 ) mixed event pairs
2
2
2
2
2
2
Gaussian
 qout
 
Rout
 qside
Rside
 qlong
Rlong
model (3-d): C ( q , k )  1  (k ) e
~
2
1
R
1
q (GeV/c)
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HBT Excitation Function of
π
STAR, PRL 87, 082301 (2001)
kT-dependence
Agree among RHIC expts.
May 6, 2004
Hanyang University
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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?
beam into screen
hydrodynamic expansion
late rescattering
time

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
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Azimuthally sensitive π HBT
qlong 
qside
qout
Rside2
 = 90°
reaction
plane
Rside (small)
Rside (large)
 = 0°
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Hanyang University
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HBT(): Centrality & kT dependence
Au+Au, √s = 200 GeV
STAR, nucl-ex/0312009
May 6, 2004
Hanyang University
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System deformation at Freeze-out
 Final state
eccentricity
from
– v2
– HBT with
respect to the
reaction plane
b

y2  x2
y2  x2
t
May 6, 2004
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Nuclear Modifications to Hard Scattering
PHENIX, PRL91, 072301 (2003); 88, 022031 (2002)
d 2 N AA /dpT dh
RAA ( pT ) 
TAA d 2 NN /dpT dh

q
q
1. Large Cronin effect at low energy
2. Large suppression at RHIC (jet quenching)
3. Is the suppression due to the medium (Initial or final state effect)?
May 6, 2004
Hanyang University
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d+Au Control Experiment
VS
Nucleus
-nucleus
collision
Proton/deuteron
-nucleus
collision
• 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
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RAA vs RdA for Identified p0
d+Au
Initial State
Effects Only
Au+Au
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
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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
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Centrality Dependence
Au + Au Experiment
d + Au Control Experiment
PHENIX, PRL91, 072303 (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
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Rcp Variable
STAR, PRL92, 052303 (2004)
Rcp=binary-collision scaled
centrality ratio
Mesons and baryons show different behaviors.
 Dependence on the number of valence quarks
 Support the quark coalescence again
May 6, 2004
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This suppression can be explained
by the parton energy loss due to
the dense & opaque medium,
Gyulassy & Wang, NPB 420, 583
(1994)
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Jet Quenching;
Azimuthal dependence
2-Particle Correlations: dN/d()
“Trigger”  = 0
trigger
away-side
near-side
STAR, PRL90, 082302 (2003)
May 6, 2004
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Disappearance of the Away-Side Jet
STAR, PRL91, 072304 (2003); 90, 082302 (2003)
p+p: 2 jets
d+Au: 2 jets
1/NtriggerdN/d()
Background subtracted
di-hadron
Au+Au peripheral
2 jets
Au+Au central
1 jet !
May 6, 2004
Near side jet
“identical”
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ppdAuAuAu
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Path Length Dependence
di-hadron, 20 - 60% central
STAR Preliminary
s NN =200 GeV
Out-of-plane
Measured
In-plane
Reflected
Suppression is larger in out-of-plane (longer path length) !
May 6, 2004
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Path Length Dependence
di-hadron, 20-40% Central
2.5  pTtrig  4 GeV/c
Out-of-plane
1  pTassoc  2.5 GeV/c
In-plane
Jet quenching is consistent with path length dependence !
May 6, 2004
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Particle Dependence of Asymmetry
2.5  pTLH  4.0 GeV/c
1.0  pTAM / B  2.5 GeV/c
10-20%
05-10%
Cent: 0-5%
40-60%
20-40%
1.1
1.0
Associated
Mesons
C
0.9
PHENIX Preliminary
0.8
1.1
1.0
Associated
Baryons
0.9
0.8
0
40
80
120
160 0
40
80
120
160 0
40
80
120
160 0
40
80
120
160 0
40
80
120
160
deg.)
Noticeable differences
in the asymmetries for
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associated baryons and mesons
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Conclusions
• Flow
– 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
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Hanyang University
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