Quarkonia measurements at STAR

1
Quarkonia measurements at STAR
Lijuan Ruan (for the STAR Collaboration) (Brookha
ven National Laboratory)

• Outline
• Motivation and introduction
• J/? results
• ? results
• Summary and outlook

2
High pT J/y in heavy ion collisions
Hot wind dissociation
J/? suppression at low pT maybe from excited
stats (?, ?c) F. Karsch, D. Kharzeev and H.
Satz, PLB 637, 75 (2006) Hot wind dissociation ?
high pT direct J/? suppression 2-component
approach dissociation recombination RAA
decreases slightly or flat with pT X. Zhao and
R. Rapp, hep-ph/07122407 RAA increase slightly
with pT including formation time and B decay X.
Zhao, WWND2008 Color singlet model RAA
increase with pT (formed out of medium) K. Farsch
and R. Petronzio, PLB 193(1987), 105 J.P.
Blaizot and J.Y. Ollitrault, PLB 199(1987),499
H. Liu, K. Rajagopal and U.A. Wiedemann PRL 98,
182301(2007) and hep-ph/0607062 M. Chernicoff, J.
A. Garcia, A. Guijosa hep-th/0607089
T. Gunji, QM08
3
Quarkonium production mechanism in pp
Whats the production mechanism at RHIC energy?

• Color singlet model (CSM) 1) ? pQCD
• Color octet model (COM) 2) ? NRQCD
• Color evaporation model (CEM) 3)
• Contribution might from
• Gluon fusion
• Heavy quark fragmentation 4)
• Gluon fragmentation 5)
• Decay feed-down
• How do we distinguish different production
• mechanism and different source contribution?

1) R. Baier et al., PLB 102, 364 (1981) 2) M.
Kramer, Progress in Particle and Nuclear Physics
47, 141 (2001) 3) H. Fritzsch, PLB 67, 217
(1977) 4) Cong-Feng Qiao, hep-ph/0202227 5) K.
Hagiwara et al., hep-ph/0705.0803
4
The STAR Detector
Run8 without any inner tracker
5
Low pT J/y in pp and CuCu at 200 GeV
J/y trigger
0 lt pT lt 5.5 GeV/c
pp 200 GeV
J/??ee-
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High pT J/y in pp at 200 GeV
EMC trigger
J/y pT
pp 2005
EMCTPC electrons hlt1, pTgt2.5 GeV/c TPC only
electrons hlt1, pTgt1.2 GeV/c
(SB)/B 24/2
3 pb-1
No background at pTgt5GeV/c
J/y pT
pp 2006
(SB)/B 54/14
11 pb-1
Reach higher pT (14GeV/c)
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J/y spectra in pp and CuCu at 200 GeV

• Significantly extend pT range of previous
  measurements in pp at RHIC to 14 GeV/c
• Agreement of charm measurements between STAR and
  PHENIX
• Consistent with Color Evaporation calculations
  (R. Vogt, Private communication)

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xT scaling in pp collisions
n is related to the number of point-like constitue
nts taking an active role in the interaction n8
diquark scattering n4 QED-like scattering

• xT scaling
• ? and proton at pTgt2 GeV/c n6.50.8 PLB 637,
  161(2006)
• J/? at high pT n5.60.2
• ?J/? production closer to 2?2 scattering
• 3. Soft processes affect low pT J/? production

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Nuclear modification factor RAA

• Double the pT range to 10GeV/c
• Consistent with no suppression at high pT
  RAA(pTgt5 GeV/c) 0.90.2
• Indicates RAA increase from low pT to high pT

• Contrast to AdS/CFT prediction
• Formed out of medium?
• Affect by heavy quark/gluon energy loss
• Decay from other particles?

2-component Approach predicted slightly increase
RAA after more consideration X. Zhao, WWND2008
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Disentangle contributions via Correlations

• J/?-hadron correlation can also shed light on
  different source contribution to J/? production
• May be used to distinguish CSM and COM

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J/y-hadron correlation
Near side correlation
Heavy quark fragmentation
Good S/B ratio makes this measurement possible
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J/y-hadron correlation in pp

• No significant near side J/?-hadron azimuthal
  angle correlation
• Constrain B mesons contribution to J/? yield
• Hints of CSM?

h-h correlation
PRL 95,152301(2005)
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Constrain bottom yields
STAR Preliminary

• pQCD predicts significant B?J/?
• correlations shows low B contribution
• can used to further constrain B yields
• constrain correlation from jet fragmentation

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Yields in near/away side

• Associated hadron spectra with leading J/?
• Away side Consistent with leading charged
• hadron correlation
  measurement (h-h) ?away-side
  from gluon or light quark fragmentation
• Near side Consistent with no associated
  hadron production B?J/? not
  a dominant contributor to inclusive J/?
• constrain J/? production
  mechanism

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J/?ccbar production puzzle
ee-, 10.6 GeV
B.L. Loffe and D.E. Kharzeev PRD 69, 014016 (2004)
Belle, PRL 89, 142001(2002)
0.82 0.15 0.14 from new analysis.
T. Uglov, EPS 2003
While CEM predict 0.049
D. Kang, et al., PRD 71, 094019 and hep-ph/0412381
NRQCD predict 0.1
K. Liu and Z. He, PRD 68, 031501 (2003)
The higher order contribution is significant and
can not be neglected.
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CSM with kt-factorization
PHENIX, PRL 92, 05180 (2004)
CSM can also describe the data with some
improvement like the kt-factorization approach
S.P. Baranov and A. Szczurek arXiv0710.1792
PRL98, 252002(2007)
CSM NLO correction is huge CSM NNLO correction is
significant for ? Jean-Phillippe Lansberg
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? results pp and AuAu at 200 GeV

• ? (1S2S3S) total yield integrated from 7 to 11
  GeV from background-subtracted mee distribution
• Peak width consistent with expected mass
  resolution
• Significance of signal is 3-4?
• Note Contribution from Drell-Yan (9) not
  subtracted

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? results pp
preliminary
Bee(ds/dy)y09128(stat.)22(syst.) pb
STAR 2006 vs200 GeV pp ??????ee- cross
section consistent with pQCD and world data RAA
in progress
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Summary

• J/? in pp and CuCu collisions
• pT spectra in pp
• extended to 14 GeV/c
• follows xT scaling with n5.6 at pTgt5 GeV/c
• J/?-hadron azimuthal correlation in pp
• no significant near side correlationconstrain
  the contribution from B?J/?X
• away-side spectra consistent with
• h-h correlation ? gluon or light quark
  fragmentation
• J/? RAA
• indication of RAA increasing at high pT
• ? in pp and AuAu collisions
• pp results consistent with pQCD and
• world data RAA in progress

• production mechanisms
• described by CEM and CSM
• soft processes affect low pT production
• constrain decay contribution
• constrain J/? production from jet contribution
  (heavy flavor and gluon)
• constrain production mechanism CSM or COM
• medium properties

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? and high-pt J/? in run8 dAu
STAR Preliminary
STAR Preliminary
STAR Preliminary
dAu data sampled luminosity 31 nb-1
pp equivalent 13pb-1

• J/? spectra
• J/?-h correlation
• Isolated J/?
• ?(2S)
• ?c

STAR Preliminary
STAR Preliminary
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Future dramatic improvement of J /? at low pT

• EMCTOFHFT (large acceptance)
• J/? production
• Different states predicted to melt at different T
  in color medium
• Charmonia (J/?), bottonia (?)

PHENIX Acceptance hlt0.35,
f2p/2 STAR TOF-Upgrade Acceptance hlt0.9,
f2p J/y yields from 1 billion minbias AuAu
events 43.8x10-9/0.040x1092920.51.80.5
144,000?0.3 v2 error sJ/y spp N
Nbin e y RAA
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High luminosity for ? high-pT J/?
RHIC II DAQ1000
Time-Of-Flight
Enhance statistics
Electron identification
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Detector upgrades HFT and MTD
Heavy Flavor Tracker
??ee- rejection Topologically reconstruct J/?
from B decay
Rejection power 16
Muon Telescope Detector
Muon identification
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Backup
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Datasets
High-pT J/y
Triggered data

• pp data sample
• 1. EMC triggered events in year 2005
• ETgt3.5 GeV
• Integrated luminosity 3 (pb)-1
• 2. EMC triggered events in year 2006
• ETgt5.4 GeV
• Integrated luminosity 11 (pb)-1
• CuCu data sample
• 1. EMC triggered events in year 2005
• ETgt3.75 GeV
• Integrated luminosity 0.9 (nb)-1
• pp-equivalent 3 (pb)-1

• pp data sample
• 1. J/? triggered events in year 2006
• Integrated luminosity 377 (nb)-1
• 2. ? triggered events in year 2006
• Integrated luminosity 9(pb)-1
• AuAu data sample
• 1. ? triggered events in year 2007
• Integrated luminosity 300(µb)-1
• pp-equivalent 12(pb)-1