production in d Au collisions at STAR

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? production in dAu collisions at STAR

• Haidong Liu
• University of California, Davis
• For the STAR Collaboration

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Outline

• Motivations
• ? measurements in pp AuAu
• STAR detectors and the ? trigger
• Electron identification
• ? signals in dAu
• Cross section and the nuclear modification
  factors
• Summary

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Motivations
Lattice QCD Calculations
Quarkonias suppression patterns ? QGP
thermometer
Dissociation temperatures of quarkonia states
hep-ph/0110406
H. Satz NPA 783(2007) 249

• For the ? production at RHIC
• co-mover absorption negligible
• recombination negligible at RHIC
• rare rate -gt need large acceptance and efficient
  trigger

A .Mocsy, 417th WE-Heraeus-Seminar,2008

• At RHIC energy
• ?(1S) no melting
• ?(2S) likely to melt
• ?(3S) melts

STAR is a powerful detector to measure ?
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? Measurements in pp AuAu
pp (QM2006)
AuAu (QM2008)
3s signal
Cross section calculation is in progress
The cross section in pp is consistent with pQCD
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STAR ? mass resolution
w/ inner material
w/o inner material

• High material runs
• Run6 pp 200GeV
• Run7 AuAu 200GeV

• Low material run
• Run8 dAu 200GeV

Its a good opportunity to measure ? in this
high luminosity and low material dAu run
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STAR detector for ? measurement

• TPC
• Acceptance ? lt 1 , 0 lt ? lt 2?
• Tracking gt momentum
• eID (ionization energy loss, dEdx)

• BEMC
• Acceptance ? lt 1 , 0 lt ? lt 2?
• eID (E/p)
• High-energy tower trigger gtessential for the
  luminosity limited measurement

? ? e e-
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STAR ? trigger (BEMC L0L2)

• L0 (hardware)
• Accepting high energy tower of ETgt4.3 GeV
• L2 (software)
• Select high energy tower cluster pair with E1gt4.5
  E2gt3.0 GeV
• Loose cut on cos? (?is the 3D opening angle)
• Cut on meev2E1E2(1-cos?)

Large acceptance BEMC L0L2 trigger is a great
di-electron trigger for luminosity limited
measurements
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Electron ID with TPCBEMC

• Use TPC for charged tracks selection
• ? trigger enhances electrons
• Use EMC for hadron rejection
• Electrons identified by dE/dx ionization energy
  loss in TPC

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? signal in dAu 200 GeV collisions
Integrated all pT

• Signal Background ? unlike-sign electron pairs
• Background ? like-sign electron pairs
• ?(1S2S3S) total yield integrated from 7 to 11
  GeV from background-subtracted mee distribution
• 172 /- 20 (stat.)
• Strong signal (8s significance)

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Efficiencies
???acc?EMC(L0L2)?2(TPC reco)?2 (eID cut )

• ?acc is geometrical acceptance
• ?EMC(L0L2) is efficiency of EMC detector and the
  trigger system
• ?(TPC reco) is efficiency of e reco in TPC
• ?(eID cut ) is efficiency of eID cuts

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? Cross-section at midrapidity
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Nuclear modification factors
0100
Consistent with Nbin scaling
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Summary and outlook

• First midrapidity measurement of ??????ee-
  cross section at RHIC in dAu collisions at
  vs200 GeV
• Sigal significance 8s
• Bee(ds/dy)y0354(stat.)nb
• RdAu 0.980.33 Rcp 1.150.40
• The cross section in dAu follows Nbin scaling
• The RAA calculation is in progress
• STAR is a powerful detector to measure ?
• Large acceptance TPCEMC
• Efficient trigger (L0L2)
• ? measurements in the future
• ? cross section in pp 500 GeV
• RHIC II high luminosity will allow separation
  of 1S, 2S, 3S states