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Probing Dense Partonic Matter at RHIC
Barbara Jacak
for thePHENIX Collaboration
Feb. 8, 2004
News from PHENIX
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Outline
Characterizing plasmas with PHENIX Initial state
pQCD via direct photonsShadowing via RdA in d+AuInitial state multiple scattering in d+Au
ThermalizationElliptic flow dependence on particle type, √s productionCharm flow
Probes of the partonic stateHeavy quark energy lossAway-side jet modificationWhat baryons tell about coupling to the medium
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Properties of plasmas
Plasma physicists always want to know (and so do we)pressure, viscosity, equation of state,thermalization time & extent
determine from collective behavior at RHIC Other useful plasma properties
radiation rate, collision frequency, conductivity, opacity, Debye screening length
what is interaction of q,g in the medum? need short wavelength strongly interacting
probe transmission probability
jet quenching via RAA high momentum q,g are our “external” probes!
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PHENIX• Collision vertex and centrality
– Beam-Beam Counters (BBC)– Zero Degree Calorimeters (ZDC)
• Tracking of Charged particle– Drift Chambers (DC)– Pad Chambers (PC1, PC2, PC3)
• , K, p, d, ... ID by Time-Of-Flight– Start timing from BBC– Stop timing from
High resolution TOF detectors (TOF)TOF from Lead Scintillator EMCal (PbSc)
• Electron ID– Ring Image Cherenkov (RICH) detectors– EMCal (PbSc, PbGl)
• Photon (0, , ...)– EMCal (PbSc, PbGl)
• Muon– Muon Tracker (MuTr)
Cathode-strip readout chamber
– Muon Identifier (MuID)Streamer (Iarocci) tube and steel
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Direct photons (p+p)
LO
NLO: BremsstrahlungpQCD works!
see talk of S. Bathe
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Direct photons in Au+Au
pQCD works too (with nuclear Sa/A(xa,r) , TA(r) + observed 0
can reliably calculate rate & distribution of short wavelength probes of hot, dense partonic matter!
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kT smearing?
data allow kT
smearing But, certainty
awaits higher statistics (currently being analyzed)
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Charm production also calculable*
* total yield scales with Ncoll.
I will return to charm again
** there is a long-standing problem with c
nucl-ex/0409028
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Charm via single e± in p+p
PHENIX preliminary
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Single e± in √sNN = 62.4 GeV Au+Au
Compatible with <Ncoll> scaling
(PHENIX compared with ISR results for p+p)
PHENIX PRELIMINARY
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Nuclear initial state effects
shadowing, saturation, multiple initial state scattering
PHENIX has a wide range of d+Au data
toolsshadowing via heavy quark or high pT hadron
productionPHENIX can probe saturation (super-shadowing…)
via rapidity dependence of hadron productionInitial state multiple scattering via dependence of
hadrons upon number of collisions per participant
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Probe cold nuclear matter by varying number of collisions.
Shadowing + initial semi-hard scatterings(Accardi, Gyulassy) reproduce the data
PRELIMINARY
Phys. Lett. B586, 244 (2004)
Very little room for additional dynamical shadowing at mid-y
Nuclear medium modifies initial state
d+Au: Cronin Effect (RdA>1): Multiple Collisions broaden pT spectrum
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PRELIMINARY
Cronin effect for protons greater than for
would not expect this from initial state
partonic multiple scattering!
pp
AuAubinaryAuAuAA Yield
NYieldR
/
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Need something else too…
Recombination?!
PROTON PRODUCTION IN D+AU COLLISIONS AND THE CRONIN EFFECT; HWA & YANG
Phys.Rev.C70:037901,2004
“Thermal
Thermal+Shower
Fragmentation (one jet)
Different jets.
“
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Muon arms probe forward rapidity
Au
d
MUON ARMS
CAN DETECT:
*stopped muons from hadron decays
* hadrons which punch thru absorber and interact in arm
study central vs. peripheral in d+Au
see talk of Anuj Purwar
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d+Au central/peripheral
Aud
Au
1.5 < pT (GeV/c) < 4.0
Suppression at forward η and enhancement in the back η.
PTH = Punch Through HadronsHDM = Hadronic Decay Muon
PHENIX nucl-ex/0411054
x~0.2-0.3
x~0.2x10-3
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Compare with BRAHMS
Overall consistent.
nucl-ex/0411054
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Color glass condensate?
Hadron Punch Through
Slightly better agreement with BRAHMS data“normal” shadowing cannot explain (R. Vogt hep-ph/0405060)
…could be sign of CGC
Kharzeev, hep-ph/0405045
Centrality, pT
dependence
~ correct
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But, recombination lurks…
shower + medium recombination → reductes soft parton density on deuteron side
Can explain fward-bward asymmetry AND RCP (protons) > RCP (mesons) at midrapidity.
Hwa, Yang and Fries nucl-th/0410111
BRAHMS data
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: does it fit with the non-strange mesons?
K+K- Au + Au @ √SNN = 200 GeV
Au+Au width & centroid as in PDG
nucl-ex/0410102
see talks of D. Pal and D. Mukhopadhyay
MixedBackground
Co
un
ts p
er 1
0 M
eV/c
2
e+e- invariant mass (GeV/c2)
e+e- @ d – Au, √s = 200 GeV
S ~ 120S/B = 1/4
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spectra & radial flow
mT – mass [GeV/c2]0 0.5 1 1.5 2 2.5 3
10-1
10-2
10-3
10-4
10-5
PHENIX preliminarysNN = 200 GeV d+Au, Min. Bias
e+e-
K+K-
Au + Au @ √sNN = 200 GeV
Au + Au @ √sNN = 200 GeV
d+Au yields & slopes: KK and ee consistent Au+Au: slopes nearly independent of Npart
but – this is at high pT
consistent with blast wave fit to , K, p
Tfo = 109 ± 2.6 MeV, T,max = 0.77 ± 0.004
nucl-ex/0410102
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v2 and scaling with nquark
stat. error onlysys. error <20% (62GeV) 15% (200GeV)
62.4 GeV Au+Au: preliminary200 GeV Au+Au, charged ,K,p PRL91, 182301 (2003) 0 : work in progress
v 2 /n
qu
ark
extend to
higher pT
pT /nquark [GeV/c]
62.4 GeV Au+Au:
scaling, v2/quark
similar to 200 GeV
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Collision energy dependence
smooth rise of v2 from AGS to SPS to RHIC energies.
v2 saturates: evidence for soft EOS? how soft?
Elliptic flow dv2/dpT vs √s
nucl-ex/0411040
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Are the v2 trends hydrodynamic?
use Buda-Lund model (nucl-th/0402036)particle emission from ellipsoidal expanding sourcev2 in terms of Bessel functions from Boltzmann distrib.
converting to transverse “rapidity”:
so v2 should have the form:
12
0
( )
( )
I wv
I w
22 0 3 01 2
20 1 1
~ 1 ..T
T k Tk kv y m
T k m k m
22 0 3 01 2
20 1 1
~ 1 ..T
T k Tk kv y m
T k m k m
2fs
T m Ty k y m 2fsT m Ty k y m
we then define a “fine
structure” variable
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The data transform: 2fsT m Ty k y m 2fsT m Ty k y m
pT (GeV/c)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
v 2
0.00
0.05
0.10
0.15
0.20
0.25
pK
s 200 GeVNNAu Au
0 1 2 3
v 2
0.00
0.05
0.10
0.15
0.20
s 200 GeVNNAu Au
p
fsTy
5 < Centrality < 30 %
K
(PHENIX)
(PHENIX)
(PHENIX)
0.0 0.5 1.0 1.5 2.0 2.5
v 2
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
fsTy
Kp
Hydro
Au Au data look like hydro!
(kaons a mystery, still)
scaling with also seen
supports scenario of rapid thermalizationKolb, et al
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Caveat: v2 & spectra vs. hydrodynamic models
proton pion
Hydro models:Teaney(w/ & w/oRQMD)
Hirano(3d)
Kolb
Huovinen(w/& w/oQGP)
nucl-ex/0410003
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How about heavy quarks? do they flow?
PHENIX measures v2 of non-photonic e±
electron ID in Au+Au via RICH + EMCALmeasure and subtract photonic sources using converter
nucl-ex/0502009
YES
v2 ≠ 0 at 90% confidence level
data consistent with heavy q thermalization
also “predicted” by Teaney
*but large errors; run4 will tell
Greco,Ko,Rapp.
PLB595, 202 (2004)
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Short wavelength probes of partonic matter
HOW is jet fragmentation modified by the medium? do heavy quarks lose energy as the light quarks do?
Kharzeev & Dokshitzer PLB519, 199 (2001): eloss smaller dead cone due to large mass decreases gluon radiationby ~20% at moderate pT
Djordjevic, Gyulassy, Wicks hep-ph/0410372: smallerdead cone, charm pT spectrum & B contribution cause RAA ~ 0.6-0.8 for 2.5< pT <4 GeV/cCronin effect & collective flow also important
Armesto, Dainese, Salgado, Wiedeman hep-ph/0501225 :smallerdead cone, g vs. q eloss differences → smaller RAA for c
Teaney: eloss significant if charm thermalizes!
coupling to the medium probes medium properties
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Non-photonic single electron spectra
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Use p+p single e± as reference → RAA
clear
evidence for
energy loss of
charm quarks
in central
Au + Au!
(NB likely to
also be some
e± from B decays)
RAA
pT (GeV/c)
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Consistent with light quarks?
RAA
pT (GeV/c)
q consistent w/ light quark eloss
non-pert.
effects on
“normal” g
radiation
data say:
same transport coefficient,
smaller hadron suppression
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jet probes of the medium
Hard scattered partons traverse the interesting stuff
Energy loss by induced gluon radiation
where does the energy go?
Modification of fragmentation outside the medium??
recombination with medium partons
radiated gluons nearby!
coneRFragmentation:
z hadron
parton
p
p
see talk of N. Ajitanand
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correlation functions of two high pT hadrons
Elliptic flow component measured vs. BBC reaction plane
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decompose to get jet pair distribution
Away-side jets broadened
non-Gaussian!
~2 dip at & peak at 1.25 rad around hard parton thru medium
integrating entire away side recovers jet partners
Casalderry, Shuryak, Teaney say 1.1 rad cone
hep-ph/0411315
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Jet partner likely for trigger baryons as well as mesons! Same side: slight decrease with centrality for baryonsDilution from boosted thermal p, pbar?
Away side: partner rate as in p+p confirms jet source of baryons!“disappearance” of away-side jet into narrow angle for both baryons and mesons
identify triggers, count partnersnucl-ex/0408007
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What’s going on?
Thermal quark recombination
Radiated gluons are collinear (inside jet cone)
Increases partner yield
Fries, Bass & Muellernucl-th/0407102
Meson triggerbaryon
Dilutes jet partner yield
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Jet partner distribution on trigger side
Corrected to jet yield according to fragmentation symmetric in Partner spectrum flatter, as expected for jet sourcePartners soften in most central collisions
Jet partners
Inclusive
nucl-ex/0408007
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Compare to hard-soft recombination
trigger & associatedHwa & Yang nucl-th/0407081
Soft-hard recomb. also explains baryon Cronin effect! No jet-correlated medium flow
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Conclusions
Direct & hard processes in AuAu calculable in pQCDwe observe nuclear shadowing at RHICno room for saturation at mid-y; forward: could bebaryon mysteries already present in d+Au
Hadron v2 trends support rapid thermalization hypothesis
theorists have homework to see how soft is EOSheavy quarks do flow (and thermalize…)
Heavy quarks lose energy in the medium!jet fragmentation is modified; lost energy excites the mediumbaryon formation in/near medium in A+A and d+A
Opacity/collision frequency, screening length await run4 analysis completion (+ theory work!)
radiation rate (low mass leptons, soft ) → PHENIX upgrades
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backup slides
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Compare to Au+Au
RAA as expected in Au+Au; d+Au slightly enhanced
p RAA scales with Ncoll in Au+Au, but higher than p+p
PRELIMINARY
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Turn to nuclear collisions: single particles
h/0 ratio shows baryons enhanced for pT < 5 GeV/c
PRELIMINARY
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yields
0 100 200 300 0 100 200 300
dN/d
y
<Npart> <Npart>(d
N/d
y) /
(2<
Np
art>
)
200 GeV d+Au (preliminary)
200 GeV Au+Au w/ centrality cut
200GeV Au+Au Min. Bias
Hor. bar : stat. err.
Box : total sys. err.
rapid rise in /participant in peripheral collisions then ~ constant per participant - as for kaons
nucl-ex/0410102
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Interacting Hadrons
Interacting Hadrons (tail)
Stopped muons (peak)
PH
3 GeV
1 GeV
3 GeV
MuID
Gap (Layer) 0 1 2 3 4
ste
el
Hadrons interactelectromagneticallyAND strongly.
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Muons from Light Meson Decays
Muon event collision vertex distribution
Muondetector
absorber
Muon pT ~ 0.85 parent pT
η > 0
Det
ecto
r
• D c = 0.03 cm Decays before absorber• c = 780 cm Most are absorbed, but some decay first • K c = 371 cm Most are absorbed, but some decay firstγcτ >> 80cm → Decay Probability nearly constant between nosecones
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FONLL Predictions
Mateo Cacciari provided a prediction using the Fixed Order Next Leading Logarithm pQCD approach
His calculation agrees perfectly with our “poor man’s” HVQLIB+PYTHIA predictions
Data exceed the central theory curve by a factor of 2-3
Possible explanations:NNLO contribution Fragmentation mechanisms
need to be studied in more details
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centrality dependence?
need to complete analysis of run4 data… first glimpse
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Pions in 3 detectors in PHENIX
Charged pions from TOF
Neutral pions from EMCAL
Charged pions from RICH+EMCAL
Cronin effect gone at pT ~ 8 GeV/c
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Subtract the underlying event
CARTOON
flow
flow+jet dN
Ntrig d
includes ALL triggers(even those with no
associated particles inthe event)
jet Measure with mixed events;Collective flow causes another correlation in them:
B(1+2v2(pTtrig)v2(pT
assoc)cos(2))
associated particles with non-flow angular
correlations -> jets!
1
combinatorial background large in Au+Au!
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2 particle correlations
Select particles with pT= 2.5-4.0GeV/c
Identify them as mesons or baryons viaTime-of-flight
Find second particle with pT = 1.7-2.5GeV/c
Plot distribution of the pair opening angles;integrate over 55°
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Thermalization? particle ratios and spectra
consistent with strongly expanding thermalized source
observed strangeness production complete chemical equilibrium
/K/p measurement in aBroad pt range
Statistical fit:Tch~ 160MeV, s~1.0Strangeness saturation at RHIC?
stronger radial flow at RHIC?
Exp
ansi
on v
eloc
ity
Tkin ~ 100 MeV<T> ~ 0.5
Chemical freezeout
Thermal freezeout
RHIC
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HBT vs. hydro models
Nobody gets HBT right!
Origin of the “HBT puzzle”
Generic explanation: Nobody does freezeout of final state right
Another explanation:Maybe we’re fooled by the extraction of the radius parameters somehow
NB: Rside source transverse radius!
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Empirical energy loss from dataF
ract
iona
l ene
rgy
loss
For power-law spectrum with A/pT
n
(we find n= 8.1 in pp)
Final spectrum = initial - <fractional shift>
<shift> due to eloss of parent partonParent pT would be:pT’ = (1+S) pT(pp)
Fractional energy loss:Sloss = 1 - 1/(1+S)
10 GeV: E/x ~ 0.5 GeV/fm
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State-of-Art; Zooming into low pT
Most realistic calculationIncluding all the contributions
We may be able to see QGP contribution in 1-3GeV/c in Run4!
Thanks to Ralf Rapp for providing theoretical points!
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Results (RAA)
Photon RAA is consistent with unity over all the centrality compared to 0 results.Clear evidence of that the yield follows thickness-scaled hard scatteringp-p reference from NLO pQCD Calculation0 RAA decreases to ~0.2 at Npart=320
Dotted line shows uncertainty of thickness functionError bars show total error (systematics + statistical) except thickness function error
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Centrality (in)dependence in d+Au collisions
PHENIX PRELIMINARY
PHENIX PRELIMINARYPHENIX PRELIMINARY
PHENIX PRELIMINARY
1/T A
B1/
T AB
1/T A
B1/
T AB
1/T
ABE
dN/d
p3 [m
b G
eV-2]
1/T
ABE
dN/d
p3 [m
b G
eV-2]
1/T
ABE
dN/d
p3 [m
b G
eV-2]
1/T
ABE
dN/d
p3 [m
b G
eV-2]
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Does Cronin enhancement saturate?
A different approach:
Intrinsic momentum broadening in the excited projectile proton:
hpA: average number of collisions:
X.N.Wang, Phys.Rev.C 61 (2000): no upper limit.
Zhang, Fai, Papp, Barnafoldi & Levai, Phys.Rev.C 65 (2002): n=4 due to proton d dissociation.
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Jets in PHENIX
Trigger:hadron with pT > 2.5 GeV/cBiased, low energy, high z jets!
Plot of associated partnersCount associated lower pT
particles for each trigger “conditional yield”
Make correlation functions→ disentangle flow and jet contributions
trigger2 particle correlationsnear side < 90°Partner from same jet
away side > 90° opposing jet
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Initial state: p+p collisions
p-p PRL 91 (2003) 241803
Good agreementwith NLO pQCD
2
/( , )
a Nf x Q
2
/( , )ch a
D z Q
Parton distribution functions
Fragmentation functions
0
0 well described by pQCD and usual fragmentation functions
To generalize for nuclei:fa/N(xa,Q2,r) fa/N(xa,Q2) .
Sa/A(xa,r) .
tA(r)
Nuclear modification to structure function (shadowing, saturation, etc.)
Nuclear thickness function
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pQCD in Au+Au? direct photons
[w/ the real suppression]
( pQCD x Ncoll) / background Vogelsang/CTEQ6
[if there were no suppression]
( pQCD x Ncoll) / ( background x Ncoll)
Au+Au 200 GeV/A: 10% most central collisions
[]measured / []background = measured/background
Preliminary
Probe calculation works!
pT (GeV/c)
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USA Abilene Christian University, Abilene, TXBrookhaven National Laboratory, Upton, NYUniversity of California - Riverside, Riverside, CAUniversity of Colorado, Boulder, COColumbia University, Nevis Laboratories, Irvington, NYFlorida State University, Tallahassee, FLFlorida Technical University, Melbourne, FLGeorgia State University, Atlanta, GAUniversity of Illinois Urbana Champaign, Urbana-Champaign, ILIowa State University and Ames Laboratory, Ames, IALos Alamos National Laboratory, Los Alamos, NMLawrence Livermore National Laboratory, Livermore, CaUniversity of New Mexico, Albuquerque, NMNew Mexico State University, Las Cruces, NMDept. of Chemistry, Stony Brook Univ., Stony Brook, NYDept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY Oak Ridge National Laboratory, Oak Ridge, TNUniversity of Tennessee, Knoxville, TNVanderbilt University, Nashville, TN
Brazil University of São Paulo, São PauloChina Academia Sinica, Taipei, Taiwan
China Institute of Atomic Energy, BeijingPeking University, Beijing
France LPC, University de Clermont-Ferrand, Clermont-FerrandDapnia, CEA Saclay, Gif-sur-YvetteIPN-Orsay, Universite Paris Sud, CNRS-IN2P3, OrsayLLR, Ecòle Polytechnique, CNRS-IN2P3, PalaiseauSUBATECH, Ecòle des Mines at Nantes, Nantes
Germany University of Münster, MünsterHungary Central Research Institute for Physics (KFKI), Budapest
Debrecen University, DebrecenEötvös Loránd University (ELTE), Budapest
India Banaras Hindu University, BanarasBhabha Atomic Research Centre, Bombay
Israel Weizmann Institute, RehovotJapan Center for Nuclear Study, University of Tokyo, Tokyo
Hiroshima University, Higashi-HiroshimaKEK, Institute for High Energy Physics, TsukubaKyoto University, KyotoNagasaki Institute of Applied Science, NagasakiRIKEN, Institute for Physical and Chemical Research, WakoRIKEN-BNL Research Center, Upton, NYRikkyo University, TokyoTokyo Institute of Technology, TokyoUniversity of Tsukuba, TsukubaWaseda University, Tokyo
S. Korea Cyclotron Application Laboratory, KAERI, SeoulKangnung National University, KangnungKorea University, SeoulMyong Ji University, Yongin CitySystem Electronics Laboratory, Seoul Nat. University, SeoulYonsei University, Seoul
Russia Institute of High Energy Physics, ProtovinoJoint Institute for Nuclear Research, DubnaKurchatov Institute, MoscowPNPI, St. Petersburg Nuclear Physics Institute, St. PetersburgSt. Petersburg State Technical University, St. Petersburg
Sweden Lund University, Lund
12 Countries; 58 Institutions; 480 Participants*
*as of January 2004