Quarkonium suppression at RHIC

1
Quarkonium suppression at RHIC

• Olivier Drapier,
• for the collaboration
• Laboratoire Leprince-Ringuet, Palaiseau, France
• IN2P3-CNRS et École polytechnique

2
Heavy-ion collisions
g
p,n
t
l
A
A
p,k
kinetic freeze-out
chemical freeze-out
hadronization
hadrons
chiral symmetry ? thermal equilib. ? chemical eq
uilib. ?
deconfinement ?
mixed phase ?
plasma
partons
Leptons Dileptons
thermalization
z
3
J/? suppression in the QGP
Open charm particles
sequential Melting
Satz, J. Phys. G32, R25 (2006)
plasma
partons
4
Heavy quarkonium production

• Onia production
• Leading order at low x gluon
  fusion
  
• Sensitive to

• Different models
• CEM, CSM, COM

• Initial state
• Parton distribution functions (PDF)
• pT broadening
• Parton energy loss in the initial state ?
• Polarization ?

• Final state
• In-medium dissociation
• In-medium recombination
• Flow ?
• Thermal enhancement ?

feed-down (e.g. B or ?c- J/y)
5
PHENIX electrons in central arm
J/? ? e e- p 0.2GeV/c ? ???

Like Sign Subtraction
6
PHENIX muon arms
J/? ? ? ?- p 2GeV/c 1.2 ???

Event Mixing Background Subtraction
7
proton-proton collisions
8
pp - J/? cross-section
(µb)
Consistent with trend of worlds data and with
the COM
but unable to differentiate between PDFs
9
J/? cross section vs rapidity

• Comparison with theoretical predictions allows
  differentiation among the available J/?
  production mechanisms
  
• Many calculations are inconsistent with the
  steepness of the slope at forward rapidity and
  the slight flattening observed at mid-rapidity
  
• Bll ?pp(J/? )1783 53 18 nb

10
Transverse momentum distributions
11
vs collision energy

• PHENIX measurements compared to
  measurements at other collision energies show a
  linear dependence on ln(vs)

12
Nucleus-nucleus collisions
13
From proton to nucleus ...

• First problem reference
• J/y normalized to ... ?
•  hard  Process
• BUT
• We dont measure NCOLL
• MODEL !
• Glauber geometry observable
• 5 4 NPART
• Number of PARTICIPANTS,
• 5 4 NCOLL
• Number of BINARY COLLISIONS

J/y or ?
Proportional to the number of binary N-N collisio
ns
PHENIX
etc
20-25
15-20
10-15
5-10
90-95
0-5
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From proton to nucleus ...

• Nuclear modification factor
• J/? production in Nucleus-Nucleus / p-p
• As a function of the collision centrality
• NPART or NCOLL
• Taking into account the number of binary
  collisions corresponding to the centrality sample

15
CuCu and AuAu results
6
AuAu PHENIX Final PRL98, 232301 (2007)
CuCu PHENIX Preliminary nucl-ex/0510051
16
From proton to nucleus ...

• Onia production
• Leading order at low x gluon
  fusion
  
• Sensitive to

• Different models
• CEM, CSM, COM

• Initial state
• Parton distribution functions (PDF)
• pT broadening
• Parton energy loss in the initial state ?
• Polarization ?

• Final state
• In-medium dissociation
• In-medium recombination
• Flow ?
• Thermal enhancement ?

17
Shadowing dAu

• Heavy flavor probe for  cold  nuclear
  effects
  
• Parton distribution functions are modified in
  nuclei
  
• e.g. in dAu collisions

Anti-shadowing
Shadowing
Nothing ?
18
Absorption in nuclear matter sabs

• Heavy flavor probe for  cold  nuclear
  effects
  
• J/? can be absorbed by inelastic diffusion on
  nucleons
  
• e sabs intuitive if J/y disappears in an
  absorbing medium of thickness L
  
• Seems to be the case _at_ SPS energies

19
Cold nuclear matter effects

• PHENIX dAu _at_ 200 GeV
• (anti)shadowing clearly visible
• sabs 1 3 mb ? Difficult to disentangle from
  shadowing
  
• Reminder 4.18mb _at_ SPS
• New dAu analysis high statistics pp to come
  soon !!
  
• Dependence with centrality
• For AuAu mirror distribution

RdAu
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RAA and cold nuclear matter effects

• CNM effects
• Gluon shadowing
• nuclear absorption
• J/y measurement in dAu collisions.
• sabs 1mb
• PRL, 96, 012304 (2006)

RAA
1
RHIC CNM effects (sabs 0, 1, 2mb at y0, y2)
R. Vogt et al., nucl-th/0507027 Acta Phys.
Hung, A25, 97 (2006)
0

• Significant suppression relative to CNM
  effects.
  
• BUT with this model for shadowing, CNM effects
  predict larger suppression at mid-rapidity, while
  data shows larger suppression at forward-rapidity

21
Comparison to NA50

• Data seems consistent between SPS and RHIC at y
  0
  
• BUT beware of CNM effects !

NA50 at SPS (0ENIX at RHIC (1.2
RHIC CNM effect (sabs 0, 1, 2mb at y0, y2)
R. Vogt et al., nucl-th/0507027
Acta Phys. Hung, A25, 97 (2006)
NA50(dN/dh) Eur. Phys. J. C35, 335 (2005)
RHIC(dN/dh) PRC. 71, 034908 (2005)
SPS CNM effect (sabs 4.18 mb)
NA50, Eur. Phys. J. C39 (2005)355
Bar uncorrelated error Bracket correlated erro
r Global error 12 and Global error 7 are n
ot shown
Normalized by NA51 pp data with
correction based on Eur. Phys. J. C35, 335 (2005
)
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Models that reproduce SPS data

• Models that reproduce NA50 results at lower
  energies ...
  
• Satz - color screening in QGP (percolation
  model) with CNM added (EKS shadowing 1 mb)
  
• Capella comovers with normal absorption and
  shadowing
  
• Rapp direct production with CNM effects
  (without regeneration)
  
• ... predict too much suppression for RHIC
  mid-rapidity !
  

23
Models that reproduce SPS data

• All predict more suppression for central
  rapidity
  
• E.g. because the comover density is higher in the
  central region
  
• Doesnt seem to be observed that way ...

Capella, Ferreiro hep-ph/0610313
24
19
Models with regeneration

• Various Suppression Recombination models
• Better matching
• Only way to accommodate less suppression at y0
• BUT recombination prop. to charm2, strongly
  depends on charm distributions, poorly known

• Calculations for mid-rapidity
• R. Rapp et al.
• PRL 92, 212301 (2004)
• Thews
• Eur. Phys. J C43, 97 (2005)
• Nu Xu et al.
• PRL97, 232301 (2006)
• Bratkovskaya et al.
• PRC 69, 054903 (2004)
• A. Andronic et al.
• NPA789, 334 (2007)

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vs centrality

• Good consistency found between the in Heavy
  Ion
  
• collisions as a function of centrality and the
  pp results

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vs centrality

• pT broadening compatible with multiple diffusion
  on nucleons (Cronin effect)
  
• In this case, proportional to L
• Data compatible with this scenario
• Compatible with one single slope from SPS to
  RHIC
  
• Flattening (e.g. due to recombination) cannot be
  ruled out ...
  

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Future ? ?
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Upsilons ?
QM05
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STAR ? vs. Theory and World Data
STAR 2006 vs200 GeV pp ??????ee- cross
section consistent with pQCD and world data
From P. Djawotho, at DNP 2007
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STAR High pT J/?
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Conclusion

• RHIC data show a strong J/? suppression beyond
  CNM effects
  
• compatible with SPS data _at_ y0
• Stronger suppression _at_ forward rapidity
• rules out  suppression-only  scenarios
• Comovers alone, sequential melting alone, J/?
  suppression in QGP alone
  
• Regeneration ?
• Strongly depends on charm distributions poorly
  known !
  
• Up to now, the only way to cope with less
  suppression _at_ y0
  
• Could account for pT behavior ?
• Cronin effect not well known
• Need more pieces of the puzzle !
• Better control of CNM effects (dAu more
  statistics to come soon !)
  
• Other resonances (?, ?c, ?) about to be
  investigated at RHIC