Transcript Quarkonium suppression at RHIC Olivier Drapier, for the collaboration Laboratoire Leprince-Ringuet, Palaiseau, France IN2P3-CNRS et École polytechnique Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007

Quarkonium suppression at RHIC
Olivier Drapier,
for the
collaboration
Laboratoire Leprince-Ringuet, Palaiseau, France
IN2P3-CNRS et École polytechnique
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Heavy-ion collisions
p,n
g
hadrons
mixed phase ?
plasma
partons
thermalization
A
kinetic freeze-out
chemical freeze-out
hadronization
chiral symmetry ?
thermal equilib. ?
chemical equilib. ?
deconfinement ?
p,k
A
t
l±
Leptons &
Dileptons
z
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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J/ψ suppression in the QGP
Open charm
particles
“sequential
Melting”
Satz, J. Phys. G32, R25 (2006)
plasma
partons
_
cc pair ~
J/y pre-resonant
state
Color screening
of
_
the cc potential
by the surrounding
color charges
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Heavy quarkonium production
 ’’Onia’’ production
 Leading order at low x
= ’’gluon fusion’’
J/y
or

 Sensitive to:
Different models
Initial state
Parton distribution
functions (PDF)
pT broadening
Parton energy loss in
the initial state ?
Polarization ?
CEM, CSM, COM
Final state
In-medium dissociation
In-medium recombination
Flow ?
Thermal enhancement ?
+ feed-down (e.g. B or c-> J/y)
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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PHENIX: electrons in central arm
J/y  e+ ep > 0.2GeV/c
|| < 0.35
  p
PHENIX
p+p 200GeV
PRL98, 232002 (2007)
Like Sign
Subtraction
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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PHENIX: muon arms
J/y  + p > 2GeV/c
1.2 < |y| < 2.2
 = p
PRL98, 232002 (2007)
PHENIX
p+p 200GeV
Event Mixing
Background
Subtraction
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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proton-proton collisions
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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(μb)
p+p -> J/ψ cross-section
PRL98, 232002 (2007)
Consistent with trend of world’s data and with the COM
but unable to differentiate between PDF’s
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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J/y cross section vs rapidity
 Comparison with theoretical predictions allows differentiation among the
available J/y 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/y )=178±3± 53 ± 18 nb
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Transverse momentum distributions
PRL98, 232002 (2007)
<pT2> = 3.59±0.06
±0.16
<pT2> = 4.14±0.18
+0.30-0.20
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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<pT2> vs collision energy
PRL98,232002 (2007)
PHENIX <pT2 > measurements compared to measurements at
other collision energies show a linear dependence on ln(√s)
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Nucleus-nucleus collisions
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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From proton to nucleus ...
 First problem : reference
J/y
or

 J/y normalized to ... ?
 « hard » Process
Proportional to the number
of binary N-N collisions
PHENIX
 BUT
 We don’t measure NCOLL
 MODEL !
 “Glauber” = geometry <-> observable
 5 + 4 = NPART
0-5 %
A
 Number of PARTICIPANTS,
 5 * 4 = NCOLL
 Number of BINARY COLLISIONS
B
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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From proton to nucleus ...
 Nuclear modification factor:
RAA =
dNJ/yAA
dNJ/yPP
x
<Ncoll>
 J/y 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
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Cu+Cu and Au+Au results
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RAA
1
Au+Au PHENIX Final: PRL98, 232301 (2007)
Cu+Cu PHENIX Preliminary: nucl-ex/0510051
0
Au+Au PHENIX Final: PRL98, 232301 (2007)
Cu+Cu PHENIX Preliminary: nucl-ex/0510051
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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From proton to nucleus ...
 ’’Onia’’ production
 Leading order at low x
= ’’gluon fusion’’
J/y
or

 Sensitive to:
Different models
Initial state
Parton distribution
functions (PDF)
pT broadening
Parton energy loss in
the initial state ?
Polarization ?
CEM, CSM, COM
Final state
In-medium dissociation
In-medium recombination
Flow ?
Thermal enhancement ?
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Shadowing: d+Au
 Heavy flavor = probe for « cold » nuclear effects
 Parton distribution functions are modified in nuclei
 e.g. in d+Au collisions :
Pb / p
d
Shadowing
Anti
Shadowing
Au
X
rapidity y
X1
J/y
South
y<0
X2
X1
X2
X1
X2
J/y
Central y < 0
Anti-shadowing
Nothing ?
Shadowing
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
J/y
North
y>0
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Absorption in nuclear matter:
abs
 Heavy flavor = probe for « cold »
nuclear effects
 J/y can be absorbed by inelastic
diffusion on nucleons
 e – <rL> abs = intuitive if J/y
disappears in an “absorbing medium”
of thickness L
 Seems to be the case @ SPS energies
Projectile
L
J/Y normal nuclear
absorption curve
Target
J/y
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Cold nuclear matter effects
 PHENIX d+Au @ 200 GeV
RdAu
RdAu
Low x2 ~ 0.003
(shadowing region)
0 mb
3 mb
Y = –1.7
Y=0
Y = +1.8
 (anti)shadowing clearly visible
 abs ~1 – 3 mb ? Difficult to disentangle
from shadowing
 Reminder: 4.18mb @ SPS
 New d+Au analysis + high statistics p+p to
come soon !!
 Dependence with centrality
 For Au+Au = mirror distribution
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
X
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RAA and cold nuclear matter effects
RAA
1
 CNM effects
 Gluon shadowing +
nuclear absorption
 J/y measurement in d+Au
collisions.
 abs ~ 1mb
 PRL, 96, 012304 (2006)
0
RHIC CNM effects
(abs = 0, 1, 2mb at y=0, y=2)
R. Vogt et al., nucl-th/0507027
Acta Phys. Hung, A25, 97 (2006)
• 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
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Comparison to NA50
NA50 at SPS (0<y<1)
PHENIX at RHIC (|y|<0.35)
PHENIX at RHIC (1.2<|y|<2.2)
 Data seems consistent
between SPS and RHIC
at y ~ 0
 BUT beware of CNM
effects !
RHIC CNM effect
(abs = 0, 1, 2mb at y=0, y=2)
R. Vogt et al., nucl-th/0507027
Acta Phys. Hung, A25, 97 (2006)
NA50(dN/d) : Eur. Phys. J. C35, 335 (2005)
Bar: uncorrelated
error
RHIC(dN/d)
: PRC. 71,
034908 (2005)
Bracket : correlated error
Global error = 12% and
Global error = 7% are not shown
SPS CNM effect (abs = 4.18 mb)
NA50, Eur. Phys. J. C39 (2005):355
Normalized by NA51 p+p data with
correction based on
Eur. Phys. J. C35, 335 (2005)
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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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)
models
AllAll
models
forfor
y=0y=0
PRL98,
PRL98, 232301
232301 (2007)
(2007)
J/y,y’,c
J/y,y’,c
... predict too much
suppression for
RHIC mid-rapidity !
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Models that reproduce SPS data
All predict more
suppression for central
rapidity
 E.g. because the comover
density is higher in the
central region
 Doesn’t seem to be
observed that way ...
Capella, Ferreiro hep-ph/0610313
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Models with regeneration
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 Various Suppression+ Recombination models
Calculations for midrapidity
• R. Rapp et al.
• PRL 92, 212301 (2004)
• Thews
• Eur. Phys. J C43, 97 (2005)
• Nu Xu et al.
• PRL97, 232301 (2006)
 Better matching:
• Bratkovskaya et al.
• PRC 69, 054903 (2004)
• A. Andronic et al.
• NPA789, 334 (2007)
 Only way to accommodate less suppression at y=0
 BUT recombination ~ prop. to charm2, strongly depends on
charm distributions, poorly known
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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<pT2> vs centrality
PRL98, 232002 (2007)
PRL98, 232301 (2007)
PRL98, 232002 (2007)
PRL98, 232301 (2007)
Good consistency found between the <pT2> in Heavy Ion
collisions as a function of centrality and the p+p results
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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<pT2> vs centrality
 pT broadening
compatible with multiple
diffusion on nucleons
(“Cronin effect”)
gluon
cc
Au SPS : dépendance linéaire de l’augmentation
du <pT2>  effet Cronin : diffusion de gluon
dans l’état initial  <pT²> = <pT²>pp + agN.L
J /y
<pT2>
 In this case,
proportional to L
 Data compatible with
this scenario
 Compatible with one
single slope from SPS
to RHIC
Au Rhic : <pT²> plat ?
2 = p 2
SPS .vs.pTRhic
T…pp + agN · L
 Flattening (e.g. due to
recombination) cannot
be ruled out ...
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Future: y’ ?
Run 6 200GeV p+p
Invariant Mass (GeV/c2)
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Upsilons ?
QM05
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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STAR  vs. Theory and World Data
preliminary
Υ  Υ'  Υ''
 dσ 
Bee  

dy

 y 0
 91  28(stat.) 22(syst.)pb
STAR 2006 √s=200 GeV p+p
++→e+e- cross section
consistent with pQCD and world
From P. Djawotho, at DNP 2007
data
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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STAR High pT J/ψ
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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Conclusion
 RHIC data show a strong J/ψ suppression beyond CNM effects
 ~ compatible with SPS data @ y=0
 Stronger suppression @ forward rapidity
 ~ rules out « suppression-only » scenarios
 Comovers alone, sequential melting alone, J/ψ suppression in QGP alone
 Regeneration ?
 Strongly depends on charm distributions … poorly known !
 Up to now, the only way to cope with less suppression @ y=0
 Could account for pT behavior ?
 Cronin effect not well known
 Need more pieces of the puzzle !
 Better control of CNM effects (d+Au: more statistics to come soon !)
 Other resonances (ψ’, Χc, Υ) about to be investigated at RHIC
Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007
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