Non-Photonic Electron-Hadron Correlations at STAR and PHENIX

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Non-Photonic Electron-Hadron Correlations at STAR
and PHENIX
Bertrand Biritz University of California, Los
Angeles
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Outline

• Motivation
• Analysis procedure
• Near-side contribution in pp collisions
• Away-side broadness in AA collisions
• Outlook

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Further supported by 3-particle correlations
Motivations
Conical Pattern in 2-Particle Correlations in
AuAu Collisions
pTtrig 2.5-4.0 GeV/c pTasso 1.0-2.5 GeV/c
Mark Horner (for STAR Collaboration) J. Phys.
G Nucl. Part. Phys. 34 (2007) S995
See STAR paper on 3-particle correlations at
arXiv0805.0622v2 (accepted by PRL)
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Near Side whats the contribution of B/D decay
to the non-photonic electrons?
trigger
Motivations
Conical Pattern in 2-Particle Correlations in
AuAu Collisions
pTtrig 2.5-4.0 GeV/c pTasso 1.0-2.5 GeV/c
What if we trigger on non-photonic electrons?
Mark Horner (for STAR Collaboration) J. Phys.
G Nucl. Part. Phys. 34 (2007) S995
Away Side in medium How does B/D lose energy?
Via conical emission?
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Study of heavy flavor via non-photonic electrons
PYTHIA

• D mesons have their directions well represented
  by the daughter electrons, above 1.5 GeV/c.
• Electrons from B decays can represent the B
  meson momentum direction well if pT gt 3 GeV/c.

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Electron ID with PHENIX

• PHENIX central arm coverage
• ? lt 0.35
• ?? 2 x p/2
• p gt 0.2 GeV/c
• typical vertex selection zvtx lt 20 cm
• charged particle tracking using
  Drift Chamber (DC) and Pad Chamber 1 (PC1)
• electron identification based on
• Ring Imaging Cherenkov detector (RICH)
  
• Electro-Magnetic Calorimeter (EMC)

Data Sample At ?sNN 200 GeV, pp collisions
in run5/6 (2006), AuAu collisions in run7
(2007).
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Electron ID with STAR

• TPC
• ? lt 1.5
• ?? 2p
• p gt 0.1 GeV/c
• particle ID
• BEMC/BSMD
• PbSc
• 20 X0
• energy and particle rejection e and h

Data Sample At ?sNN 200 GeV, pp collisions
in run5/6 (2006), dAu collisions in run8
(2008), CuCu collisions in run5 (2005), AuAu
collisions in run7 (2007).

• Time Projection Chamber (TPC)
• Barrel Electro-Magnetic Calorimeter (BEMC)
• Barrel Shower Maximum Detector (BSMD)

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Electron signal and background
Photonic electrons
Non-photonic electrons

• Decay photon conversions
• p0??? ? g g,
• g ? e e- in material
• Main background
• Dalitz decays
• p0??? ? g e e-
• Direct photon conversions
• Small but could be significant at high pT

• Heavy flavor electrons
• D/B ? e X
• Weak Kaon decays
• Ke3 K ? p0 e ?e
• lt 3 contribution in pT gt 1 GeV/c
• Vector Meson Decays
• w, ?, f??J??, ? ? ee-
• lt 2-3 contribution in all pT

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PHENIX
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Identifying the Photonic Background

• The invariant masses of the OS and SS e-pairs
  have different distributions.
• Reconstructed photonic electrons are the result
  from subtracting SS from OS.
• Photonic electrons are (reconstructed photonic
  electrons) / e
• e is the background reconstruction efficiency
  calculated from simulations.

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Procedure to Extract the e-h Correlations
Semi-inclusive electrons
?fnon-pho ?fsemi-incl ?fSameSign (1/eff
-1)(?fOppSign ?fSameSign)
Each element has its own corresponding ?f
histogram.
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Near-Side contribution in pp
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Non-photonic e-h correlations in pp 200GeV

• Clear azim. correlation is observed around near
  and away side.
• Fitting measured dn/df distribution from B and D
  decays, we can estimate B decay contribution to
  non-photonic electron.

B
D
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B contribution to non-photonic e in pp 200GeV
Almost fifty-fifty B and D contributions to
non-photonic es at 5.5 lt pT lt 9 GeV/c and FONLL
prediction is consistent with our data within
errors.
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B contribution to non-photonic e in pp 200GeV
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Large bottom quark energy loss?

• RAA for non-photonic electrons is consistent with
  hadrons.
• This indicates a large energy loss
• for not only charm but also bottom
• quarks.

non-? e
hadron
With the measurements of r _at_ pp and RAA, we can
derive a relationship between
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• together with models
• Dominant uncertainty is normalization in RAA
  analysis
• B meson is also suppressed
• prefer Dissociate (II) and
• Resonance (III) model (large b energy loss)

pT gt 5 GeV/c
STAR preliminary
I Djordjevic, Gyulassy, Vogt and Wicks, Phys.
Lett. B 632 (2006) 81 dNg/dy 1000 II Adil
and Vitev, Phys. Lett. B 649 (2007) 139 III
Hees, Mannarelli, Greco and Rapp, Phys. Rev.
Lett. 100 (2008) 192301
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Near-side Summary

• Non-photonic e-h correlations have been measured
  in pp collisions to retrieve B and D
  contributions to non-photonic electrons up to
  pT9 GeV/c.
• Comparable B and D contributions for electron pT
  from 5.59 GeV/c.
• FONLL prediction and the eB/(eBeD) results are
  consistent with each other within errors.
• The measured B/D ratio would imply considerable
  b quark energy loss in medium based on RAA
  measurement from central AuAu collisions. One
  more measurement is needed or r
  for AA.

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Away-side broadness in AA
pp and dAu collisions serve as a reference for
the cold nuclear matter
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Non-photonic e-h correlations in dAu 200 GeV
3 lt pTtrig lt 6 GeV/c 0.15 lt pTasso lt 0.5 GeV/c
STAR Preliminary
Non-photonic e-h azimuthal correlation is
measured for p range, and open markers are
reflections. The away-side correlation can be
well described by PYTHIA calculations for pp
i.e. no medium effects seen.
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Non-photonic e-h correlations in CuCu 200 GeV
0 20 3 lt pTtrig lt 6 GeV/c 0.15 lt pTasso lt
0.5 GeV/c
Upper limits of v2 used are 60 of hadron v2
values measured with the v2EP method
(equivalent to v22).
On the away side, theres a broad structure or a
possible double-hump feature, even before v2
subtraction. PYTHIA fit has a big ?2.
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Possible interpretations
The away side in e-h is similar to what has been
observed in h-h correlations, and consistent with
Mach Cone calculations etc. The charm jet
deflection provides an alternative interpretation.
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Non-photonic e-h correlations in AuAu 200 GeV
0 20 3 lt pTtrig lt 6 GeV/c 0.15 lt pTasso lt
0.5 GeV/c
STAR Preliminary
Upper limits of v2 used are 80 of hadron v2
values measured with the v2EP method.
Non-photonic e-h correlation is broadened on the
away side. PYTHIA fit has a big ?2.
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Away-side Summary

• Using the dAu collision as a reference, the
  shape of non-photonic e-h azimuthal correlation
  function is found to be modified in central CuCu
  and AuAu collisions due to the presence of the
  dense medium created in these collisions.
• Away-side Hint of a broad structure, similar
  shape to that from h-h correlations.
• Induced by heavy quark interaction with the
  dense medium?
• Quantitative measure and investigation of the
  nature of the possible conical emission pattern
  will require more statistics. DAQ1000 will help
  us there. Should also try 3-particle correlations.

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Thank you
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Outlook
Large associated particle yields on the near side
leave open questions collective medium
excitation by heavy quarks?
Momentum kick model, Cheuk-Yin Wong
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Back up slides
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HQ Production Mechanism

• Due to large mass, HQ productions are considered
  as point-like pQCD processes
• HQ is produced at the initial via leading gluon
  fusion, and sensitive to the gluon PDF
• NLO pQCD diagrams show that Q-Qbar could be not
  back-to-back in transverse plane
• We need to study this smearing effect with models

?? ? ?
?? ? ?
flavor creation
?? ? 0
gluon splitting
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PYTHIA simulations
B
Each pt bin is weighted with their relative
yields, and then they are summed up.
For each pt bin, the non-photonic e-h
correlations B_corr and D_corr are combined
according to Bs and Ds relative contributions
to the non-photonic electrons (eBB_corr
eDD_corr) / (eBeD)
D
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Electron ID in STAR
PuritydAu, CuCu, AuAu above 98 for 3 lt pT lt
6 GeV/cpp collisions above 98 for 3 lt
pT lt 6 GeV/c 80 for 9 GeV/c.
calibrated Log(dE/dx)
With BEMC and BSMD, the electron peak is enhanced
in the energy loss distribution, and we obtain a
very pure electron sample.
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PYTHIA simulations weighted with CuCu yields
3 lt pTtrig lt 6 GeV/c 0.15 lt pTasso lt 0.5 GeV/c
B
D
Here we assume the B/D contribution in CuCu is
similar to that in pp. Even if they are not
similar, we dont expect the double-hump without
a medium.