Perspectives on Quarkonia Physics at RHIC II

1
Perspectives on Quarkonia Physics at RHIC II

• Thomas Ullrich, BNL
• Yale University, April 16-17, 2004
• Workshop on RHIC-II Physics and Perspectives for
  New Comprehensive Detector

2
The Original Idea
Matsui Satz (PLB 178 (1986) 416 J/? suppression
by QGP Color screening of static potential
between heavy quarks
3
The Original Idea
Matsui Satz (PLB 178 (1986) 416 J/? suppression
by QGP Color screening of static potential
between heavy quarks
D. Kharzeev and H. Satz, Phys. Lett. B477 (2000)
Hard gluons needed for breaking J/? not
available in hadron gas S. Digal et al., Phys.
Rev. D 64, 094015 (2001) C.-Y. Wong, Phys. Rev. C
65, 034902 (2002) Calculations using lattice
potentials sequential suppression ?, ?c
dissolves below TC J/? dissolves at 1.2 TC
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and its Confirmation

• CERN/SPS ?s ? 17 GeV
• mid-rapidity
• large statistics (beyond RHIC)

5
Experimental Status 2004

• Study pA in detail ? absorption in nuclear matter

Ebinding(Y) 50 MeV Ebinding(?c) 200
MeV Ebinding(J/Y) 640 MeV
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Experimental Status 2004

• Detailed pA studies ? absorption in nuclear
  matter
• Study trigger (ET)

• wiggle is gone
• suppression w.r.t. normal
• nuclear absorption remains

7
and Evolving Theories
A. Capella, D. Sousa, nucl-th/0303055
A.P.Kostyuk, M.I. Gorenstein, H. Stocker, W.
Greiner, Phys. Lett B 531, 195-202

• Various alternative models which also reproduce
  data
• Statistical coalescence model (also needs
  enhanced open charm)
• Absorption by comoving matter

8
Remaining Questions

• Charm production at SPS ?
• Feeddown from ?c states ?
• xF dependence ?
• important means to constrain theory
• and understand nuclear effects
• and learn about production mechanism

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and the Big Blow

• QM2004 F. Karsch News from Lattice QCD

Free energy of a thermal medium due to the
presence of static quark-antiquark pairs
F itself often interpreted as heavy quark
potential at finite T and used in model
calculations but change in entropy needs to be
taken into account (F E - TS) Energy and
entropy contributions to F at different?qq
separations important. The r-dependent entropy
contribution makes a direct use of F in potential
models questionable.
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and the Big Blow ?
J/Y dissociates for 1.6 TC lt T lt 1.9 TC rather
abrupt disappearance of J/Y
J/Y gradually disappears for T gt 1.5 TC J/Y
strength reduced by 25 at T 2.25 TC
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Now What ?

• The charmonium ground state (J/Y) persist in
  the QGP as well defined resonances with no
  significant change in their zero temperature
  masses at least up to T 1.5 Tc, gradually
  disappear for T gt 1.5 Tc and are gone at 3 Tc.
• F. Karsch, hep-lat/0403016

But Used Maximum Entropy Method still needs
further studies So far the width is not
calculated (only position and amplitude) Width
is likely to increase ? Dima J/Y still can
dissolve in a short time (1 fm/c) at
RHIC F. Karsch (QM2004) Entire charmonium
discussion was based on lattice calculations in
quenched QCD. We need a much larger computer to
do better!
QCD on Lattice (2-flavor) Phase transition at
TC 173?8 MeV, eC (6?2) T 4 0.70 ? 0.27
GeV/fm3 RHIC Lattice e/T4 10 ? 95
GeV/fm3 for 3TC 520 MeV 6 GeV/fm3 for
1.5TC At RHIC energies, central AuAu
collisions From Bjorken estimates via ET and
Nch e gt 5 GeV/fm3 Calculations of energy loss
of high-pT particles e 15 GeV/fm3 Hydro
models assuming thermalization give ecenter
25 GeV/fm3
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Quarkonium Studies in HEP

• Tevatron (?s 1.8 TeV)
• CDF huge improvement from run II
• J/Y, ? cross-section down to pT0
• Polarization measurement of J/Y, Y, ? soon
• ?c contribution measured
• still all in ylt0.4 (0.6)

Solve puzzle from fixed target low polarization
for Y(1S) but high for Y(2S), Y(3S)
J/Y
?(1S) ?(2S) ?(3S)
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Quarkonium Studies in HEP

• Tevatron (?s 1.8 TeV)
• D0
• s for y lt 1.8 !
• J/Y, Y, ?c1, ?c2
• ?(1S,2S,3S)

Summer 2002 Results

4.8 pb-1 of data
30 systematic uncertainty
Luminosity 114 pb -1
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Quarkonium Studies in HEP

• Hera-B
• pA (?s42 GeV)
• J/Y / Y production ratios
• pT, xF -0.4 0.1, cos? differential
  distributions
• ?c/ J/Y ratio
• Belle, BaBar
• ee- ?? ?cc?cc puzzle s(ee??ccY)/s(ee?XY) ? 0.6
• B ? X(3872) K (?cJ(2P),?DD molecular
  state, )
• question the success of NRQCD

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Quarkonium Studies in HEP

• There is a large community (HEP) studying
  quarkonia to a large degree
• tremendous flow of new results and excellent
  measurements
• currently more issues raised than answered ?
  makes it interesting
• Production is well measured but theoretically not
  understood (as is charm production in general)
• The good old octet-model is in question
• NRQCD ?
• At high ?s (CDF/D0) heavy quark production
  mechanism might be different from that at lower
  ?s
• are results from Tevatron relevant for RHIC
  energies?
• Theres a huge gap for studies of charmonia in
  hadronic collisions between fixed target (38 GeV
  and 1.8 TeV) RHIC is right in between

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Quarkonium Measurements at RHIC

• AA
• the major goal suppression as signature of QGP
• Thermometer for early state
• Tdiss(Y) lt Tdiss(?(3S)) lt Tdiss(J/Y) ?
  Tdiss(?(2S)) lt Tdiss(?(1S))
• pp
• Interesting in itself
• no nuclear effects (production pure)
• close ?s gap (fixed target ? CDF,D0)
• needed as baseline for pA, AA
• Spin DG via J/Y
• pA
• needed to study nuclear effects
• Rate of rare processes increased by Aa compared
  to pp

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AA at RHIC

• For a full understanding of charmonium
  suppression
• understand nuclear effects
• absorption, shadowing
• from pA compared to pp
• important xF, x1, x2 dependence
• suppression vs. recombination
• pT, centrality dependence
• contribution from feeddown (? states)
• measure at a minimum in pA
• understand co-mover absorption
• ? less affected
• centrality, reaction plane, and pT dependence
• need to understand charm production
• Ultimate measurement (dream?) v2,
  suppression vs. reaction plane

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Need Good Open Charm Measurement
SPS ?s 17 GeV
RHIC ?s 200 GeV
At RHIC open charm production provides reference
and may be the only mean to understand charmonium
suppression (same gluon conditions in the initial
stage)
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Quarkonium Measurements

• Golden decay mode
• Y(1S, 2S), ?(1S, 2S) ? l l-
• ?c ? J/Y g, ?b ? ? g
• mm-
• clean trigger
• experiments have usually higher statistics than
  ee-
• not the best when low pT is important
• ee-
• trigger hard for J/Y (no problem for ?)
• larger background than mm-

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Requirements for 3rd Generation Detector

• High Rate
• Large acceptance ? rate xF coverage

Pythia 6.2
Pythia 6.2
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Requirements for 3rd Generation Detector

• High Mass Resolution (close to CDF)
• Efficient Trigger (? Level-2)

CDF ? ? m m- Tracking chamber in 1.4 T field
resolution 8.5 _at_ 4.9 GeV
PRL 75 (1995) 4358
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Requirements for 3rd Generation Detector

• ? ? J/Y(?) g measurements require
• highly granular E.M Calorimeter at least at
  mid-rapidity
• probably only feasible in pp, pA, peripheral AA
• need simulations here
• large acceptance
• Reduce hadronic background
• high e/h possible with good calorimetry and PID
  up to 10-20 GeV/c
• situation better for muons anyhow
• Good measure of reaction plane
• easy with ZDCSMD

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Rates at RHIC-II

• Assume here
• large acceptance (hlt3)
• one channel only (ee- or mm-)
• 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
• sAA spp (AB)a

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Rates at RHIC-II

• AuAu min bias rates
• R(J/Y) 27 Hz
• R(Y) 1 Hz
• R(?(1S)) 0.01701 Hz
• R(?(2S)) 0.00297 Hz
• R(?(3S)) 0.00324 Hz
• AuAu, 30 weeks, 50 efficiency
• 2.7108 J/Y
• 1107 Y
• 170100 ?(1S)
• 29700 ?(2S)
• 32400 ?(3S)
• pp
• loose factor (AB)a
• gain Lpp/LAA 60,000

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Summary

• In terms of quarkonia physics RHIC-II is not too
  far behind LHC
• s(LHC)/s(RHIC) 9 (GRV-HO) 25 (MRS-D1)
• RHIC-II 5 ? higher L
• RHIC gt 5 times longer running
• Measuring just J/Y is not enough to extract a
  physically meaningful result ? AA, pp, pA as
  function of pT, xF, cos?, centrality, reaction
  plane
• Given a 3rd generation detector and RHIC-II
  luminosity allow a world class measurement in pp,
  pA, AA
• Enough statistics to allow the study of
  production vs. pT, xF, cos?, centrality,
  reaction plane
• Quarkonia in polarized pp might open a whole new
  opportunity unique to RHIC (I know too little
  about it for this talk)