Measurement of Heavy Quark production at RHIC-PHENIX

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Measurement of Heavy Quark production at
RHIC-PHENIX

• Yuhei Morino
• CNS, University of Tokyo

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1.Introduction

• RHIC is for the study of extreme hot and dense
  matter.
• pp, dAu, CuCu, AuAu collision
• vs 22.4, 62, 130, 200 GeV A.

• Heavy quarks (charm and bottom) is produced in
  initial collision
• ?good probe for studying property of the medium.
• small energy loss and large thermal equilibration
  time are expected due to their
  large mass.

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2.PHENIX experiment

• PHENIX central arm
• h lt 0.35
• Df 2 x p/2
• p gt 0.2 GeV/c
• Charged particle tracking analysis using DC and
  PC ? p
• Electron identification
• Ring Imaging Cherenkov detector (RICH)
  
• Electro- Magnetic Calorimeter (EMC)
  ? energy E

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3.Heavy quark measurement at PHENIX
electron/muon from semileptonic decay
direct measurement D?Kp, D?Kpp
Meson D,D0
Mass 1869(1865) GeV
BR D0 --gt Kp (3.85 0.10)
BR --gt e X D 17.2, D0 6.7
p
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3.2 Result of pp at ?sNN 200 GeV
Inclusive electron ( g conversion, p daliz,etc
and heavy quark )
Background subtraction
Non-photonic electron (charm and bottom)

• scc 567 57(stat) 224(sys) mb
• FONLL Fixed Order plus Next to Leading Log pQCD
  
• Central value for
• data/FONLL predictions 1.7
• ( reasonable value)

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3.3 Result of AuAu at ?sNN 200 GeV
PHENIX PRL98 173301 (2007)
Heavy flavor electron compared to binary scaled
pp data (FONLL1.71) Clear high pT suppression
in central collisions
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3.4 Nuclear Modification Factor RAA
large suppression!
PHENIX PRL98 173301 (2007) Djordjevic, PLB632 81
(2006)

• Radiative energy loss
• does not describe!.
• dead cone effect

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3.5 Non-photonic electron v2
pQCD fail PRB637,362
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3.6 comparison with models.
various models exist.

• pQCD radiative E-loss with
• 10-fold upscaled transport coeff.
• elastic pQCD D resonances
• coalescence
• 2-6 upscaled pQCD elastic

behavior of bottom differ from charm ?c/b
separation is necessary for further discussion.
These calculations suggest that DHQ
((36)/2pT..near quantum bound) are required to
reproduce the data.
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4. B contribution to non-photonic electron
FONLL

• FONLL
• Fixed Order plus Next to Leading Log pQCD
  calculation
• Large uncertainty on c/b crossing 3 to 9 GeV/c

Experimental determination of c?e/b?e is one of
most important next steps
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Heavy quark measurement at PHENIX
electron/muon from semileptonic decay
D ?e K n partial reconstruction
p
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5 c?e/b?e via e-h correlation
unlike sign e-h pairs contain large background
from photonic electrons. ?like sign pair
subtraction (Ntag is from semi-leptonic decay)
Ntag Nunlike - N like
From real data analysis
Nc(b)?e is number of electrons from charm
(bottom) Nc(b)?tag is Ntag from charm (bottom)
edata can be written by only charm and bottom
component
From simulation (PYTHIA and EvtGen)
The tagging efficiency is determined only decay
kinematics and the production ratio of
D(B)hadrons to the first order(85).

• production ratios (D/D0, Ds/D0 etc)
• contribution from NOT D(B) daughters

Main uncertainty of ec and eb ?
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5.2 c?e/b?e via e-h correlation
theoretical uncertainty is NOT included.
Year5 pp ?s200GeV data set is used
comparison of data with simulation
(0.55.0 GeV) pt(e) 25GeV/c c2 /ndf 58.4/45
_at_b/(bc)0.34
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5.3 c?e/b?e via e-h correlation
Year5 pp ?s200GeV data set is used
(b?e)/(c?eb?e) as a function of electron pt
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Heavy quark measurement at PHENIX
direct measurement D0?Kp-p0 D0?Kp-
Meson D,D0
Mass 1869(1865) GeV
BR D0 --gt Kp- 3.85 0.10
BR D0 --gt Kp-p0 14.1 0.10
BR --gt e X 17.2(6.7)
BR --gt m X 6.6
p
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6. Direct measurement of D0
D0?Kp-p reconstruction

• Year5 pp ?s200GeV data set is used
• Observe 3s significant signal in pT D range 5
  15 GeV/c
• No clear signal is seen for pT D lt 5 GeV/c
• The signal is undetectably small for pT D gt 15
  GeV/c
• Signal is fitted with parabola(B) gaussian(S)

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Momentum Dependence
6.2 Direct measurement of D0
D0?Kp-p reconstruction

• Observe clear peak in all pT bins from 5 GeV/c
  to 10 GeV/c
• Fits are parabola gaussian
• Background is uniform within fitting range

Analysis to determine invariant cross section is
on going.
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6.3 Direct measurement of D0
D0?Kp- reconstruction with electron tag
Year5 pp ?s200GeV data set is used
real event mixing event
back ground subtracted
tag

• observe D0 peak
• Analysis to determine invariant cross
• section is on going

reconstruct
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Summary and outlook

• A large suppression pattern and azimuthal
  anisotropy
• of single electron has been observed in AuAu
  collisions
• at vsNN200GeV.
• b?e/(c?e b?e) has been studied in pp
  collisions at
• vs 200GeV via e-h correlation for further
  discussion.
• ? analysis for more statistics and high pt
  extension
• is on going
• Clear peak of D0 meson observed in pp collisions
  at
• vs 200GeV in D0?K p- p0 and D0?K p-
  channels.
• ?Analysis to determine invariant cross section
  is on going.
• The results of direct measurement will be
  compared with the results of measurement via
  semi-leptonic decay

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back up
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Singnal and Background
Photonic Electron

• Photon Conversion
• Main photon source p0??? ? gg
• In material g ? ee- (Major contribution of
  photonic electron)
• Dalitz decay of light neutral mesons
• p0??? ? g ee- (Large contribution of photonic)
• The other Dalitz decays are small contributions
• Direct Photon (is estimated as very small
  contribution)
• Heavy flavor electrons (the most of all
  non-photonic)
• Weak Kaon decays
• Ke3 K ? p0 e ?e (lt 3 of non-photonic in pT gt
  1.0 GeV/c)
• Vector Meson Decays
• w, ?, f??J?? ? ee- (lt 2-3 of non-photonic in
  all pT.)

Non-photonic Electron
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Background Subtraction Cocktail Method

• Most sources of background
• have been measured in PHENIX
• Decay kinematics and
• photon conversions can be reconstructed by
  detector simulation
• Then, subtract cocktail of all background
  electrons from the inclusive spectrum
• Advantage is small statistical error.

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Background Subtraction Converter Method
We know precise radiation length (X0) of each
detector material The photonic electron yield can
be measured by increase of additional material
(photon converter ) Advantage is small
systematic error in low pT region Background in
non-photonic is subtracted by cocktail method
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Consistency Check of Two Methods
Both methods were checked each other
Left top figure shows Converter/Cocktail ratio of
photonic electrons Left bottom figure shows
non-photon/photonic ratio
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4. Analysis(2)
From simulation (PYTHIA and EvtGen)
charm ec 0.0364 - 0.0034(sys) bottom eb
0.0145 - 0.0014(sys)
Electron pt 25GeV/c Hadron pt 0.45.0GeV/c
unlike pair like pair
(unlike-like) / of ele
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5. Result (electron Pt 23GeV/c)
theoretical uncertainty is NOT included.
comparison of data with simulation
(0.55.0 GeV) pt(e) 25GeV/c c2 /ndf 58.4/45
_at_b/(bc)0.34 pt(e) 23GeV/c c2 /ndf 34.3/22
_at_b/(bc)0.28
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5. Result (electron Pt 34GeV/c)
theoretical uncertainty is NOT included.
comparison of data with simulation
(0.55.0 GeV) pt(e) 25GeV/c c2 /ndf 58.4/45
_at_b/(bc)0.34 pt(e) 23GeV/c c2 /ndf 34.3/22
_at_b/(bc)0.28 pt(e) 34GeV/c c2 /ndf 13.4/22
_at_b/(bc)0.66
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5. Result (electron Pt 45GeV/c)
theoretical uncertainty is NOT included.
comparison of data with simulation
(0.55.0 GeV) pt(e) 25GeV/c c2 /ndf 58.4/45
_at_b/(bc)0.34 pt(e) 23GeV/c c2 /ndf 34.3/22
_at_b/(bc)0.28 pt(e) 34GeV/c c2 /ndf 13.4/22
_at_b/(bc)0.66 pt(e) 45GeV/c c2 /ndf 21.9/22
_at_b/(bc)0.75
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6.Discussion
Collisional dissociation in hot and dense matter?

• ? heavy quarks can fragment
• inside the medium and can
• be suppressed by dissociation

Input b?e/c?e
suppression of non-photonic electron is not so
strong as prediction by collisional dissociation
model.
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Open Charm in pp STAR vs. PHENIX

• PHENIX STAR electron spectra both agree in
  shape with FONLL theoretical prediction
• Absolute scale is different by a factor of 2

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• Fit e-h correlation with PYTHIA D and B
• Data shows non-zero
• B contribution

Bottom !
pp 200 GeV
STAR QM2006
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Non-photonic electron v2 measurement
page4

• Non photonic electron v2 is given as

(1)
(2)
v2e Inclusive electron v2 gt Measure
RNP (Non-? e) / (? e) gt Measure

• v2 ?.e Photonic electron v2
• Cocktail method (simulation) stat. advantage
• Converter method (experimentally)

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Inclusive electron v2
page6

• inclusive electron v2 measured w.r.t reaction
  plane
• converter --- increase photonic electron
• photonic non-photonic e v2 is different

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Photonic e v2 determination
page7
v2 (p0)
R N X-gte/ N?e
pTlt3 p (nucl-ex/0608033) pTgt3 p0 (PHENIX run4
prelim.)
decay

• photonic electron v2
• gt cocktail of photonic e v2

photonic e v2 (Cocktail)

• good agreement
• converter method
• (experimentally determined)