Marzia Rosati
mrosati@iastate.edu
Iowa State University
Third Workshop on Quarkonium
IHEP, Beijing China
October 15, 2004
Marzia Rosati - ISU
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SPS
CERN, Geneva
Pb+Pb
158 AGeV
RHIC
BNL, New York
Au+Au
100+100 GeV
LHC
CERN, Geneva
Pb+Pb
3.3 + 3.3 TeV
e/T4
energy density
Hunting the Quark Gluon
Plasma
by Measuring Quarkonium
SPS
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RHIC
QGP
LHC
hadron gas
TC ~ 170 MeV
temperature
 New Quarkonium Measurements at SPS: NA60
 New Quarkonium Measurements at RHIC: PHENIX
 Future Opportunities at RHIC and LHC
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Charmonium as a Probe of QGP
 Matsui and Satz predicted J/y production
suppression in Quark Gluon Plasma
because of color screening
c
c
Color Screening
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The NA50 experiment
A closed-geometry
muon spectrometer
experiment
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J/y suppression from p-A to Pb-Pb collisions
Measured / Expected
 The J/y production is suppressed in Pb-Pb collisions with respect
to the yields extrapolated from proton-nucleus data
 anomalous suppression
……… Lots of open questions  NA60
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What’s original in NA60:
measuring dimuons in the target region
muon trigger and tracking
beam tracker
ZDC
targets
magnetic field
silicon telescope
in a 2.5 T dipole
hadron absorber
Z-vertex of the interaction determined by
the pixel telescope with ~ 200 µm accuracy
Indium beam
Vertex transverse coordinates determined with
better than 20 mm accuracy from the pixel telescope
and beam tracker
7 In targets
158 A GeV
Beam
tracker
station
target box
windows
z-vertex (cm)
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J/y production in Indium-Indium collisions
after muon track matching
Background
s(J/y) : 105  70 MeV
matching rate ~ 70%
Charm
J/y
y’
DY
A multi-step fit (max likelihood) is performed:
a) M > 4.2 GeV : normalize the DY
b) 2.2<M<2.5 GeV: normalize the charm (with DY fixed)
c) 2.9<M<4.2 GeV: get the J/y yield
(with DY & charm fixed)
Marzia Rosati - ISU
DY yield = 253 ± 16
1964 ± 126 in range 2.9–4.5 GeV
J/y yield = 35626 ± 361
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J/y / Drell-Yan in Indium-Indium collisions
B s(J/y) / s(DY) = 19.6 ± 1.3
for L = 6.8 fm or Npart = 128
 0.85 ± 0.06
w.r.t. the normal
nuclear absorption
Projectile
J/y
L
Target
all data rescaled to 158 GeV
L= mean length of the path of the
(cc) system through nuclear matter
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PHENIX Detector
Event characterization
detectors in middle
Two central arms for
measuring hadrons,
photons and electrons
Two forward arms for
measuring muons
J/yee in central arms
electron measurement in range:
||  0.35
pe  0.2 GeV/c
Marzia Rosati - ISU
J/ymm : forward arms
muon measurement in range:
1.2 < || < 2.4
pm  2 GeV/c
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J/Y Measurement Planned at RHIC
 p-p : study of production mechanism and cross sections
 Color evaporation model, Color singlet model, Color octet model
 Polarization, Rapidity dependence (electron and muon channels)
 Production of J/Y, Y',.. states
 Base line for pA and AA
 p(d)-A : study of "normal nuclear effects": shadowing and energy
loss
 Nuclear dependence of s(J/Y): A or sabs (nuclear absorption)
 Base line for AA
 A-A : study of "medium effect" in high density matter
 J/Y suppression : signature of QGP (Matsui/Satz)
 J/Y formation by c quark coalescence?
 Comparisons between various collision species are very important.
 Studies done via both dielectron and dimuon channels in PHENIX.
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J/Y in Run 2 p-p Collisions
m+m–
e+e–
Phys.Rev.Lett.92,
051802,2004
Results
consistent
with shapes
from
various models
and PDF.
Take the PYTHIA
shape to extract
our crosssection
Integrated cross-section :
234 ± 36 (stat) ± 34 (sys) ± 24(abs) μb
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d-Au Collisions
Eskola, Kolhinen, Vogt hep-ph/0104124
South Muon Arm
North Muon Arm
d
PHENIX μ, North
PHENIX m, SOUTH
Au
Central Arm
PHENIX e
 PHENIX measurements cover different ranges of the Au parton
momentum fraction where shadowing and anti-shadowing are
expected
 All expected to see pT broadening
 dE/dx not expected to be significant effect at RHIC energies
 Overall absorption expected
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J/Y in Run 3 d-Au Collisions
In RUN3, we accumulated ~3nb-1 d-Au
collisions.
m+mm±m±
North Arm
dAu
780 J/ψ’s
s ~ 165 MeV
 combinatorial background is subtracted using the like-sign pairs
 physical background (open charm/Drell-Yan) is fitted using an exponential
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Cross section versus pT
J/Y  m+mJ/Y  m+m-
High x2 ~ 0.09
Low x2
~ 0.003
<pT2> =
<pT2>dAu – <pT2>pp
1.77 ± 0.35 GeV2
1.29 ± 0.35 GeV2
(preliminary)
pT is broadened for dAu
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dAu/pp versus pT
pT broadening comparable
to lower energy
(s = 39 GeV in E866)
s dA  s pp 2197 )

Marzia Rosati - ISU
Low x2
~ 0.003
High x2
~ 0.09
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J/Y Rapidity Distribution in dAu and pp
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dAu/pp versus rapidity
 compared to lower s
RdA
Low x2 ~ 0.003
(shadowing region)
1st J/ψ’s at large
negative rapidity!
Klein,Vogt, PRL 91:142301,2003
Kopeliovich, NP A696:669,2001
 Data favors (weak) shadowing + (weak) absorption ( > 0.92)
 With limited statistics difficult to disentangle nuclear effects. We
will need another dAu run! (and more pp data also)
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Run2 AuAu
Phys.Rev.C69, 014901,2004
y = 1.0
Coalescence model
(Thews et al)
y = 4.0
Stat. Model
(Andronic et al.)
Absorption model
(Grandchamp et al.)
 Disfavor models with enhancement relative to binary collision
scaling. Cannot discriminate between models that lead to
suppression relative to binary collision scaling.
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Simple expectation for AuAu J/ψ’s
based on nuclear dependence observed in dAu
• Renormalize model predictions to
dAu measurement (top panel).
• Then reverse RdAu and multiply
by itself (bottom panel)
• Variations between models not
too large at mid-rapidity, but
substantial in the large negative or
positive rapidity regions. Better
models (physics understanding)
might help, but a higher statistics
dAu baseline, especially in the mm
regions is needed.
• 2004 AuAu run:
~50 times more data (than RUN2)
and we already see c lear J/Y
signals
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Near future at RHIC
 Full exploration of J/Y production versus “Nbinary”
 Look forward to future runs with high luminosity where also
studies for different collision species and with varying energy can
be made
 Upcoming run in December 2004 CuCu collisions and long p-p run
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PHENIX Upgrade
 Ultimately we want to
detect open charm
“directly” via displaced
vertices
 Development of required
Si tracking for PHENIX
well underway
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RHIC-II Luminosity Upgrade
RHIC-II:
L = 5·1032 cm-2 s-1 (pp)
L = 7-9·1027 cm-2 s-1 = 7-9 mb-1 s-1 (AuAu)
hadr. min bias: 7200 mb 8 mb-1 s-1 = 58 kHz
30 weeks, 50% efficiency  Ldt = 80 nb-1
100% reconstruction efficiency
Assume here: sAA = spp (AB)
 Au+Au, 30 weeks, 50% efficiency produced number of events
 2.7·108 J/Y
 1·107 Y’
 170100 (1S)
 29700 (2S)
 32400 (3S)
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The Physics Landscape:
Pb+Pb Collisions SPS->RHIC->LHC
d
Extrapolation of RHIC results
favors low values
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LHC Heavy Ions
ALICE e+e-
ALICE μ+μ-
CMS
ATLAS
J/y
2.1x104
8.0x105
3.7x104
2.5x104

1.4x104
5.0x103
2.6x104
2.1x104
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Summary
 The good and bad news: the phenomenology of charmonium in
nuclear collisions is richer than anyone supposed
 There is enough interesting physics to keep us busy
 Things are not as simple as first supposed
 The goal of the field has shifted from “discovering the quark-gluon
plasma” to “characterizing the nuclear medium under extreme
conditions”
 This is a plus – we’ve moved past presupposing how things will
behave and towards measuring and understanding what really
happens
 Charmonium is a critical probe in this wider effort
 New data from RHIC and NA60 is right around the corner
 Experimental program will continue at LHC
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