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Recent Measurements of Charmonium in Heavy Ion Collisions. Marzia Rosati Iowa State University. Third Workshop on Quarkonium IHEP, Beijing China October 15, 2004. QGP. SPS. RHIC. 4. energy density e /T 4. LHC. hadron gas. T C ~ 170 MeV. temperature.

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marzia rosati mrosati@iastate edu iowa state university

Recent Measurements of

Charmonium in Heavy Ion Collisions

Marzia Rosati

Iowa State University

Third Workshop on Quarkonium

IHEP, Beijing China

October 15, 2004

hunting the quark gluon plasma by measuring quarkonium





energy density e/T4


hadron gas

TC ~ 170 MeV


Hunting the Quark Gluon Plasmaby Measuring Quarkonium


  • New Quarkonium Measurements at SPS: NA60
  • New Quarkonium Measurements at RHIC: PHENIX
  • Future Opportunities at RHIC and LHC
charmonium as a probe of qgp
Charmonium as a Probe of QGP
  • Matsui and Satz predicted J/y production suppression in Quark Gluon Plasma because of color screening
the na50 experiment
The NA50 experiment

A closed-geometrymuon spectrometer


j y suppression from p a to pb pb collisions


J/y suppression from p-A to Pb-Pb collisions
  • The J/y production is suppressed in Pb-Pb collisions with respect to the yields extrapolated from proton-nucleus data

 anomalous suppression

Measured / Expected

……… Lots of open questions  NA60

what s original in na60 measuring dimuons in the target region

muon trigger and tracking

magnetic field

7 In targets


target boxwindows

Beam tracker station

Z-vertex of the interaction determined by the pixel telescope with ~ 200 µm accuracy

Vertex transverse coordinates determined with better than 20 mm accuracy from the pixel telescope and beam tracker

z-vertex (cm)

hadron absorber

Indium beam

158 A GeV


What’s original in NA60: measuring dimuons in the target region

silicon telescopein a 2.5 T dipole

beam tracker



DY yield = 253± 161964 ± 126in range 2.9–4.5 GeV

J/y yield = 35626 ± 361

J/y production in Indium-Indium collisions


after muon track matching


s(J/y) : 105  70 MeVmatching rate ~ 70%





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)


all data rescaled to 158 GeV

J/y / Drell-Yan in Indium-Indium collisions


B s(J/y) / s(DY) = 19.6 ± 1.3for L = 6.8 fm or Npart = 128

 0.85 ± 0.06w.r.t. the normal nuclear absorption






L= mean length of the path of the

(cc) system through nuclear matter

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

J/ymm: forward arms

muon measurement in range:

1.2 < || < 2.4

pm 2 GeV/c

PHENIX Detector
j y measurement planned at rhic
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/, ',.. states
    • Base line for pA and AA
  • p(d)-A : study of "normal nuclear effects": shadowing and energy loss
    • Nuclear dependence of (J/): A or abs (nuclear absorption)
    • Base line for AA
  • A-A : study of "medium effect" in high density matter
    • J/ suppression : signature of QGP (Matsui/Satz)
    • J/ formation by c quark coalescence?
    • Comparisons between various collision species are very important.
    • Studies done via both dielectron and dimuon channels in PHENIX.
j y in run 2 p p collisions
J/Y in Run 2 p-p Collisions


Results consistent

with shapes from

various models and PDF.

Take the PYTHIA

shape to extract

our cross-section

Integrated cross-section :

234 ± 36 (stat) ± 34 (sys) ± 24(abs) μb


Phys.Rev.Lett.92, 051802,2004

d au collisions
d-Au Collisions

North Muon Arm

South Muon Arm

Eskola, Kolhinen, Vogt hep-ph/0104124

  • 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



Central Arm



j y in run 3 d au collisions



North Arm


780 J/ψ’s

 ~ 165 MeV

J/Y in Run 3 d-Au Collisions

In RUN3, we accumulated ~3nb-1 d-Au collisions.

  • combinatorial background is subtracted using the like-sign pairs
  • physical background (open charm/Drell-Yan) is fitted using an exponential
cross section versus p t

J/  +-

High x2 ~ 0.09

Low x2

~ 0.003

Cross section versus pT

<pT2> =

<pT2>dAu – <pT2>pp

1.77 ± 0.35 GeV2

1.29 ± 0.35 GeV2


J/  +-

pT is broadened for dAu

dau pp versus p t
dAu/pp versus pT

Low x2

~ 0.003

pT broadening comparable

to lower energy

(s = 39 GeV in E866)

High x2

~ 0.09

dau pp versus rapidity

compared to lower s

Klein,Vogt, PRL 91:142301,2003

Kopeliovich, NP A696:669,2001

dAu/pp versus rapidity


Low x2 ~ 0.003

(shadowing region)

  • 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)

1st J/ψ’s at large negative rapidity!

run2 auau

Dy = 1.0

Coalescence model (Thews et al)

Dy = 4.0

Stat. Model (Andronic et al.)

Absorption model (Grandchamp et al.)

Run2 AuAu

Phys.Rev.C69, 014901,2004

  • Disfavor models with enhancement relative to binary collision scaling. Cannot discriminate between models that lead to suppression relative to binary collision scaling.
simple expectation for auau j s based on nuclear dependence observed in dau
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  regions is needed.
  • 2004 AuAu run:

~50 times more data (than RUN2) and we already see clear J/Y signals

near future at rhic
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
phenix upgrade
PHENIX Upgrade
  • Ultimately we want to detect open charm “directly” via displaced vertices
  • Development of required Si tracking for PHENIX well underway
rhic ii luminosity upgrade
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)a
  • Au+Au, 30 weeks, 50% efficiency produced number of events
    • 2.7·108 J/Y
    • 1·107 Y’
    • 170100 (1S)
    • 29700 (2S)
    • 32400 (3S)


The Physics Landscape: Pb+Pb Collisions SPS->RHIC->LHC

Extrapolation of RHIC results favors low values

  • 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