Full Reconstruction of h

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Full Reconstruction of h Correlated with High PT
h and Identified Baryons and Mesons from STAR

• Jason Glyndwr Ulery
• Purdue University
• For the STAR Collaboration

Outline Motivation Charged-Charged
Correlations Identified Trigger Correlations 3
Particle Correlations Summary
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Motivation

• Want to create and study QGP
• State of deconfined, thermalized quarks and
  gluons predicted by QCD at high energy density.
• Jet
• Can be calculated in pQCD and thus are well
  calibrated in a vacuum.
• Are expected to be modified by the medium and can
  therefore give information on the properties of
  the medium.

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AuAu, pp and dAu
4.0ltPTTriglt6.0 GeV/c

• dAu and pp similar
• Implies jet suppression not an initial nuclear
  effect.
• AuAu suppressed on away side for higher
  associated pT.
• AuAu enhanced for inclusive associated pT.

2.0ltPTAssocltPTTrig GeV/c
0.15ltPTAssoclt4.0 GeV/c
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Mean PT

• ltptgtpt-weighted correlation / number
  correlation.
• ltpTgt is more robust.
• Some of the systematic errors cancel.
• Dip in middle of away side in central AuAu.
• Appears more thermalized with medium.

5
Mean PT Centrality Dependence.

• Mean pT decreases with centrality in the away
  side.
• Lower in core in central AuAu.

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Conical flow?
STAR data background subtracted trigger pT
2.5-4 GeV/c, associated pT 1.0-2.5 GeV/c
PHENIX data background subtracted trigger pT
2.5-4.0 GeV/c, associated pT 1.0-2.5
GeV/c Etalt0.35
0-5
5-10
STAR Preliminary
20-40
10-20
?f
?f
40-60
60-80
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Baryon/Meson
PHENIX, PRL 91, 172301 (2003)

• Greatly enhanced baryon over meson ratio in
  central AuAu relative to pp.
• Ratio nicely described by coalescence/
  recombination.
• But simple coalescence ? no angular correlations
• Identified trigger particle jets can give insight
  into this puzzle.

M. Lamont (STAR), QM2004
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Particle Identification in the TPC

e p K P
Log dE/dx

• Particle identification from TPC dE/dx
  distribution after the relativistic rise.
• Fit with Gaussians fixing kaon yield from
  measured p/k0s.
• Select high dE/dx particles as pions and low
  dE/dx particles as protons/anti-protons.
• NSigma p (dE/dx-predicted p dE/dx) /resolution

Log pT
STAR Preliminary
NSigma p
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Identified Trigger in dAu and AuAu

• 50 Proton
• 50 Anti-Proton
• 95 p
• 95 p-
• Charged

• 50 Proton/Anti-Proton
• 95 p

3ltPTTriglt4 GeV/c
0.15ltPTAssoclt3.0 GeV/c
?f
?f
?f
STAR Preliminary
2.0ltPTAssoclt3.0 GeV/c
AuAu 0-5 Most Central
dAu MinBias
Similar correlation functions for particle and
anti-particle. Hint of larger away correlation
for baryon than meson.
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Strange Triggers
3ltpTTriggerlt3.5 GeV/c 1ltpTAssociatedlt2.0 GeV/c

• ?
• Anti-?
• KS0

• Similar correlations for ?, anti-? and K0s
  triggers.
• V2 and background not subtracted.

STAR Preliminary
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Spectra and Near Side Yield
AuAu 3ltpTTriggerlt4 GeV/c
Near Side 0-5

• 50 p/pbar
• 95 p
• Charged

• Spectra shapes are similar for different trigger
  particle species.
• Hint of split between baryons and mesons in the
  near side yield at high pT.

1/NTriggerdN/dpT
STAR Preliminary
AuAu 0-5 1.0ltpTAssociatedlt2.0
pTAssociated
Away Side 0-5

• 50 p/pbar
• ?
• ?bar
• 95 ?
• K0s

Nch/NTrigger
1/NTriggerdN/dpT
STAR Preliminary
STAR Preliminary
pTAssociated
pTTrigger
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Is there conical flow?
Df2
3-particle correlation
Df1
hard-soft-corr soft-bkgd.
flow modulated background
Df2
soft-soft-corr in underlying event.
Df1
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Hard-Soft-Soft Correlation Analysis
3ltPTTriggerlt4 1ltPTAssociatedlt2
Raw Signal
1/NTrigger (dN/d(?f))2

• Trigger particle chosen.
• Distributions of pairs of associated particles
  ?f1 f1 -ftrigger and ?f2 f2 -ftrigger
• Mixed events modified by flow and subtracted
• 1 2v21v2triggercos2(f1 -ftrigger)
  2v22v2triggercos2(f2-ftrigger)
  2v21v22cos2(f1-f2)
• Cross terms (hard-soft and soft-soft in
  background) is subtracted.

Mixed Events With Flow
Hard-Soft
STAR Preliminary
Soft-Soft
Final Signal
?f
AuAu 0-10
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pp and dAu
pp 2ltPTTriggerlt4 1ltPTAssociatedlt2

• Appears elongated along the diagonal axis in dAu
• Possibly kT broadening

1/NTrigger (dN/d(?f))2
STAR Preliminary
?f
dAu 2ltPTTriggerlt4 1ltPTAssociatedlt2
?f
?f
?f

• dAu
• 3ltpTTriggerlt4
• 1ltPTAssociatedlt2
• away sS/2 0.89 0.11
• sD 0.69 0.05
• near sD 0.66 0.07

STAR Preliminary
?f
?f
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Conical Flow? 3-Particle Correlation
Three regions on away side center (p, p)
0.4 corner (p1,p1) 0.4 x2 cone (p1,p-1)
0.4 x2
difference in AuAu average signal per
radian2 center corner 0.3 0.3 (stat)
0.4 (syst) center cone 2.6 0.3 (stat)
0.8 (syst)
dAu and AuAu elongated along diagonal kT
effect, and deflected jets? Distinctive
features of conical flow are not seen in
present data with these pT windows.
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3 Particle V2
3ltPTTriggerlt4 1ltPTAssociatedlt2 0-10
4 Particle Cumulant V2

• Previous plots used average of 4 particle
  cumulant and reaction plane v2.
• Correlation is robust with v2.

STAR Preliminary
Reaction Plane V2
?f
?f
?f
STAR Preliminary
?f
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Summary

• Two particle angular correlation systematics
• Broader correlation, softer pT and partial
  thermalization
• Dip at p in ltpTgt as a function of ?f
• Identified trigger particle correlations
• Little difference between different trigger
  particle species found.
• Three particle angular correlations
• Appears elongated along diagonal in dAu and
  AuAu.
• Appears inconsistent with conical flow.

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62.4 GeV/c AuAu
0.15ltpTAssoclt4.0

• Similar to 200 GeV/c on away side.
• Reduced on the near side due to trigger bias.

STAR Preliminary
4.0ltpTTriggerlt6.0
2.0ltpTAssoclt4.0
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CuCu

• AuAu 200 GeV/c
• CuCu 200 GeV/c

0.15ltpTAssoclt4

• Constant background subtracted.
• V2 has not been subtracted

STAR Preliminary
4ltpTTriggerlt6
2ltpTAssoclt4
STAR Preliminary
?f
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dE/dx (ns p)
STAR Preliminary

• Ratio consistent along ns p

ns p

• Near
• Away
• Middle

STAR Preliminary
Triggered Events/Mixed Events

ns p
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AuAu Working Plot
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dAu Working Plot
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dAu Numbers

• Peak-Corner 0.0620.0060.001
• Peak-Cone 0.0710.0060.002

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Near Side ?? - ?f Correlations
AuAu seems to sit on a pedestal in ??.
3ltPTTriglt6 GeV/c 2ltPTAssocltPTTrig GeV/c
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Near Side Gaussian Widths and Yield

• Significant broadening for low pT triggers for
  near side ??.
• Same Gaussian ?? peak yield for all collision
  types.
• Underlying reasons not fully understood.

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hlt0.35 vs hlt1
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with f acceptance cut