Marzia%20Rosati

1
Recent Measurements of Charmonium in Heavy Ion
Collisions

• Marzia Rosati
• mrosati_at_iastate.edu
• Iowa State University

Third Workshop on Quarkonium IHEP, Beijing
China October 15, 2004
2
Hunting the Quark Gluon Plasmaby Measuring
Quarkonium
Outline

• New Quarkonium Measurements at SPS NA60
• New Quarkonium Measurements at RHIC PHENIX
• Future Opportunities at RHIC and LHC

3
Charmonium as a Probe of QGP

• Matsui and Satz predicted J/y production
  suppression in Quark Gluon Plasma because of
  color screening

4
The NA50 experiment
A closed-geometrymuon spectrometer experiment
5
J/y suppression from p-A to Pb-Pb collisions
NA38/NA50

• 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
6
Whats original in NA60 measuring dimuons in
the target region
NA60
silicon telescopein a 2.5 T dipole
beam tracker
targets
7
J/y production in Indium-Indium collisions
NA60
after muon track matching
Background
s(J/y) 105 ? 70 MeVmatching rate 70
J/y
Charm
DY
y
A multi-step fit (max likelihood) is
performeda) M gt 4.2 GeV normalize the DY
b) 2.2ltMlt2.5 GeV normalize the charm (with DY
fixed)
c) 2.9ltMlt4.2 GeV get the J/y yield
(with DY charm fixed)
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J/y / Drell-Yan in Indium-Indium collisions
Projectile
B s(J/y) / s(DY) 19.6 1.3for L 6.8 fm or
Npart 128
? 0.85 0.06 w.r.t. the normal
nuclear absorption
J/y
L
Target
preliminary
NA60
L mean length of the path of the (cc) system
through nuclear matter
9
PHENIX Detector
10
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.

11
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
ee
Phys.Rev.Lett.92, 051802,2004

• Integrated cross-section
• 234 36 (stat) 34 (sys) 24(abs) µb

12
d-Au Collisions
North Muon Arm
South Muon Arm
Eskola, Kolhinen, Vogt hep-ph/0104124
Au
d
Central Arm
PHENIX µ, North PHENIX m, SOUTH
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

13
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

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Cross section versus pT
?ltpT2gt ltpT2gtdAu ltpT2gtpp 1.77 0.35
GeV2 1.29 0.35 GeV2 (preliminary)
J/? ? ??-

• pT is broadened for dAu

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dAu/pp versus pT
Low x2 0.003

• pT broadening comparable
• to lower energy
• (?s 39 GeV in E866)

High x2 0.09
16
J/Y Rapidity Distribution in dAu and pp
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dAu/pp versus rapidity
RdA
Low x2 0.003 (shadowing region)
1st J/?s at large negative rapidity!

• Data favors (weak) shadowing (weak) absorption
  (? gt 0.92)
• With limited statistics difficult to disentangle
  nuclear effects. We will need another dAu run!
  (and more pp data also)

18
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.

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Simple expectation for AuAu J/?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 c lear J/Y signals

20
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

21
PHENIX Upgrade

• Ultimately we want to detect open charm
  directly via displaced vertices
• Development of required Si tracking for PHENIX
  well underway

22
RHIC-II Luminosity Upgrade

• RHIC-II
• L 51032 cm-2 s-1 (pp)
• L 7-91027 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

• AuAu, 30 weeks, 50 efficiency produced number
  of events
• 2.7108 J/Y
• 1107 Y
• 170100 ?(1S)
• 29700 ?(2S)
• 32400 ?(3S)

23
The Physics Landscape PbPb Collisions
SPS-gtRHIC-gtLHC
Extrapolation of RHIC results favors low values
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LHC Heavy Ions
ALICE ee- ALICE µµ- CMS ATLAS
J/? 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 weve 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