quarkonium suppression at rhic
DESCRIPTION
Quarkonium suppression at RHIC. Olivier Drapier, for the collaboration Laboratoire Leprince-Ringuet, Palaiseau, France IN2P3-CNRS et École polytechnique. Heavy-ion collisions. g. t. p,n. l ±. A. A. p ,k. kinetic freeze-out. chemical freeze-out. hadronization. - PowerPoint PPT PresentationTRANSCRIPT
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Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007 1
Quarkonium suppression at RHIC
Olivier Drapier,
for the collaboration
Laboratoire Leprince-Ringuet, Palaiseau, FranceIN2P3-CNRS et École polytechnique
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Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007 2
Heavy-ion collisionsp,n
z
partonspartons
plasmaplasma
mixed phase ?mixed phase ?
thermalization
hadronization
kinetic freeze-out
chiral symmetry ?thermal equilib. ?chemical equilib. ?deconfinement ?
,k
At
hadronshadrons
l±
chemical freeze-out
Leptons &Dileptons
A
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Quarkonium suppression at RHIC, OD@QWG07, DESY, October 18, 2007 3
J/ψ suppression in the QGP
partonspartons
plasmaplasma
Open charm
particles
cc pair ~ J/pre-
resonant state
_Color screening
of the cc potential by the
surrounding color charges
_
Satz, J. Phys. G32, R25 (2006)
“sequentialMelting”
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Heavy quarkonium production
’’Onia’’ production Leading order at low x
= ’’gluon fusion’’
Sensitive to:
Final stateIn-medium dissociationIn-medium recombinationFlow ?Thermal enhancement ?
Initial stateParton distribution functions (PDF)pT broadeningParton energy loss in the initial state ?Polarization ?
J/or
+ feed-down (e.g. B or c-> J/)
Different modelsCEM, CSM, COM
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PHENIX: electrons in central arm
PRL98, 232002 (2007)
Like SignSubtraction
J/ e+ e-
p > 0.2GeV/c
|| < 0.35
PHENIXp+p 200GeV
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PHENIX: muon arms
PHENIXp+p 200GeV
PRL98, 232002 (2007)
Event MixingBackgroundSubtraction
J/ + -
p > 2GeV/c
1.2 < |y| < 2.2 =
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proton-proton collisions
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p+p -> J/ψ cross-section
PRL98, 232002 (2007)
Consistent with trend of world’s data and with the COMbut unable to differentiate between PDF’s
(μb)
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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/ )=178±3± 53 ± 18 nb
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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
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<pT2> vs collision energy
PHENIX <pT2 > measurements compared to measurements at
other collision energies show a linear dependence on ln(√s)
PRL98,232002 (2007)
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Nucleus-nucleus collisions
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From proton to nucleus ... First problem : reference
J/ normalized to ... ?
« hard » Process
BUT We don’t measure NCOLL
MODEL ! “Glauber” = geometry <->
observable
5 + 4 = NPART Number of PARTICIPANTS,
5 * 4 = NCOLL
Number of BINARY COLLISIONS
J/or
0-5 %
5-10 %10-15 %15-2
0 %
20-2
5 %
90-95 %
etc…
PHENIX
A
B
Proportional to the numberof binary N-N collisions
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RAA =dNJ/
AA
dNJ/PP <Ncoll>x
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
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6
Au+Au PHENIX Final: PRL98, 232301 (2007) Cu+Cu PHENIX Preliminary: nucl-ex/0510051
Cu+Cu and Au+Au results
1
RAA
0
Au+Au PHENIX Final: PRL98, 232301 (2007) Cu+Cu PHENIX Preliminary: nucl-ex/0510051
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From proton to nucleus ...
’’Onia’’ production Leading order at low x
= ’’gluon fusion’’
Sensitive to:
Final stateIn-medium dissociationIn-medium recombinationFlow ?Thermal enhancement ?
Initial stateParton distribution functions (PDF)pT broadeningParton energy loss in the initial state ?Polarization ?
J/or
Different modelsCEM, CSM, COM
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Heavy flavor = probe for « cold » nuclear effects Parton distribution functions are modified in nuclei
e.g. in d+Au collisions :Pb / p
X
AntiShadowing
Shadowing
X1 X2
J/ Northy > 0
X1X2
J/Southy < 0
X1X2
J/Central y < 0
d
Au
rapidity y
Anti-shadowing ShadowingNothing ?
Shadowing: d+Au
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Absorption in nuclear
matter:abs Heavy flavor = probe for « cold »
nuclear effects J/ can be absorbed by inelastic diffusion
on nucleons
e – <L> abs = intuitive if J/ disappears
in an “absorbing medium” of thickness L Seems to be the case @ SPS energies
J/ normal nuclear absorption curve
J/
L
Projectile
Target
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Cold nuclear matter effects
PHENIX d+Au @ 200 GeV
(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
X
Y = +1.8
Y = 0
Y = –1.7
0 mb
3 mb
Low x2 ~ 0.003(shadowing
region)
RdAu
RdAu
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CNM effects Gluon shadowing +nuclear absorption J/ measurement in d+Au
collisions.
abs ~ 1mb PRL, 96, 012304 (2006)
1
RAA
0
RHIC CNM effects (abs = 0, 1, 2mb at y=0, y=2)R. Vogt et al., nucl-th/0507027Acta 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
RAA and cold nuclear matter effects
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Data seems consistent between SPS and RHIC at y ~ 0
BUT beware of CNM effects !
Normalized by NA51 p+p data with correction based on Eur. Phys. J. C35, 335 (2005)
SPS CNM effect (abs = 4.18 mb) NA50, Eur. Phys. J. C39 (2005):355
RHIC CNM effect (abs = 0, 1, 2mb at y=0, y=2)R. Vogt et al., nucl-th/0507027Acta Phys. Hung, A25, 97 (2006)
Comparison to NA50
NA50(dN/d) : Eur. Phys. J. C35, 335 (2005) RHIC(dN/d) : PRC. 71, 034908 (2005)Bar: uncorrelated errorBracket : correlated errorGlobal error = 12% andGlobal error = 7% are not shown
NA50 at SPS (0<y<1)PHENIX at RHIC (|y|<0.35)PHENIX at RHIC (1.2<|y|<2.2)
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PRL98, 232301 (2007)
Rapp
Capella
Satz
J/,’,c
All models for y=0
Satz
Rapp
Capella
J/,’,c
All models for y=0 PRL98, 232301 (2007)
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 !
Models that reproduce SPS data
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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
Models that reproduce SPS data
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Various Suppression+ Recombination models
Better matching: Only way to accommodate less suppression at y=0
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)
19Models with regeneration
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<pT2> vs centrality
Good consistency found between the <pT2> in Heavy Ion
collisions as a function of centrality and the p+p results
PRL98, 232002 (2007) PRL98, 232301 (2007)
PRL98, 232002 (2007) PRL98, 232301 (2007)
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pT broadening compatible with multiple diffusion on nucleons (“Cronin effect”)
In this case, <pT2> 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 ...
Au SPS : dépendance linéaire de l’augmentation du <pT
2> effet Cronin : diffusion de gluon dans l’état initial <pT²> = <pT²>pp + gN.L
Au Rhic : <pT²> plat ?
SPS .vs. Rhic …
pT2 = pT
2pp + gN · L
cc/J
gluon
<pT2> vs centrality
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Future: ’ ?
Run 6 200GeV p+p
Invariant Mass (GeV/c2)
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QM05
Upsilons ?
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pb22(syst.)28(stat.)91dy
dσB
'Υ'Υ'Υ
0y
ee
STAR 2006 √s=200 GeV p+p ++→e+e- cross section consistent with pQCD and world data
preliminary
STAR vs. Theory and World Data
From P. Djawotho, at DNP 2007
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STAR High pT J/ψ
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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