Jet-like Correlations between forward- and mid-rapidity

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Jet-like Correlations between forward- and
mid-rapidity

• Fuqiang Wang
• For the STAR Collaboration

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FTPC associated with TPC trigger
trigger on main TPC high pT particles (? lt
1) and look at FTPC associated particles (2.7 lt
? lt 3.9).
trigger
assoc.
assoc.
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Why do we want to do it?

• Jet correlations are measured in the main TPC
  (? lt 1). Significant modification has been
  observed.Is there jet correlation at forward
  rapidity? Hwa, Yang, nucl-th/0605037.If there
  is, is the correlation different from
  mid-rapidity?
• could be different due to different pathlengths.
• could be identical if Bjorken boost invariance.

STAR, PRL 95, 152301 (2005)
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Why do we want to do it?

• Probing different kinematics, and g vs. q jets?

g
g
x0.05
g
g
g
q
x0.05
x0.7
x0.05
q
g
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FTPC v2 correction
FTPC v2 STAR, Phys. Rev. C 72, 014904 (2005).
Centrality 70-20

• Different methods give similar v2 results for the
  FTPC data.
• Parameterize v2 in pT and h.
• Centrality dependence measured by STAR
  (preliminary).

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Au-side / d-side difference
htriglt1, 2.7lthassoclt3.9
dN/dDf
Df
corrected for efficiencyacceptance. normalized
per trigger particle. Background normalized to
near-side Dflt1.
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AuAu minimum bias
htriglt1, 2.7lthassoclt3.9 3ltpTtriglt10 GeV/c,
0.2ltpTassoclt 2 GeV/c
Normalization fixed at Df1lt0.2
Background normalization uncertainty in dashed
lines.
raw signal
dN/dDf
Major systematic uncertainties from v2 MTPC v2
v2RP and v24 bracket the uncertainty. FTPC
v2 from v22. uncertainty assumed to be as same
as MTPC v2 uncertainty. Conservative estimate.
bkgd subtracted
Near-side consistent with zero. Broad away-side
correlation.
Df
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AuAu centrality variation
htriglt1, 2.7lthassoclt3.9 3ltpTtriglt10 GeV/c,
0.2ltpTassoclt 2 GeV/c
dN/dDf
Near side consistent with zero. Away-side
broad correlation in central collisions.
Df
Normalization fixed at Df1lt0.2. Systematic
uncertainty plotted for 10-0 data.
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Double-Gaussian fit
Systematic errors from v2 uncertainties.
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Compare FTPC to MTPC
3ltpTtriglt4 GeV/c FTPC 0.2ltpTassoclt 2 GeV/c MTPC
0.2ltpTassoclt 3 GeV/c
Away-side correlations are very similar.
dAu
AuAu 80-60
AuAu 10-0
Df
Df
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Inclusive and correlated dN/dh
inclusive yield PHOBOS, PRL93, 082301 (2004)
correlated yield within Df-plt2.1
h
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Summary

• Sizeable away-side jet correlation signal in FTPC
  with a TPC trigger particle.
• Correlation magnitude smaller at forward rapidity
  than at mid-rapidity.
• dAu correlated yield in Au-direction 2 x
  d-direction.
• Near-side h ridge extended to forward
  rapidity?Systematic uncertainty too large to
  conclude.
• Away-side correlation broadens with centrality.
• three-particle correlation analysis?
• Correlation shapes similar mid-
  forward-rapidity
• dE/dx so large that the e or pathlength does not
  really matter?
• dE/dx so large that q- and g-jet difference does
  not really matter?

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v2 parameterization
v2 ()
v2 ()
C1-exp-(pT/A)B
Dexp-(h/E)2/2
h
pT (GeV/c)
v2(centrality, h, pT) v2cent(centrality)
v2h(h) v2pT(pT)
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eta smearing
eta 2.7, 3.3, 3.9 ? theta 2, 4, 8
degree