Transcript Document 7239545

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.
•p+p, d+Au, Cu+Cu, Au+Au collision
•√s = 22.4, 62, 130, 200 GeV A.
 flow & energy loss ?
 insight into the
property of the medium
•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| < 0.35
 Df = 2 x p/2
– p > 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
K
direct measurement:
DKp, DKpp
D0
p+


D0
c
K

c
Meson
D±,D0
Mass
1869(1865) GeV
BR D0 --> Kp
(3.85 ± 0.10) %
BR --> e +X
D±: 17.2, D0: 6.7 %
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3.2 Result of p+p at sNN = 200 GeV
Inclusive electron
( g conversion, p daliz,etc
and heavy quark )
PRL, 97, 252002 (2006)
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)
Upper limit of FONLL
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3.3 Result of Au+Au at sNN = 200 GeV
PHENIX PRL98 173301 (2007)
MB
0%~
Heavy flavor electron
compared to binary
scaled p+p data
(FONLL*1.71)
Clear high pT
suppression
in central collisions
~92%
p+p
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3.4 Nuclear Modification Factor: RAA
1 dN AA / dpt
RAA ( pt ) 

N coll dN pp / dpt
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
Greco, Ko, Rapp: PLB 595 (2004) 202
pQCD fail [PRB637,362]
data suggests non-zero charm v2
 charm is strongly coupled to the matter.
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3.6 comparison with models.
PLB649(2007)139
Collisional
dissociation
various
models
exist.
•
be RAA
ce RAA
heavy quarks can fragment
inside the medium and can
pQCD
radiative E-loss
with
be suppressed
by dissociation
10-fold upscaled transport coeff.
behavior
of bottom
differ
• elastic pQCD
+ D resonances
from
charm
+ coalescence
c/b separation is necessary
•for
2-6further
upscaled
pQCD elastic
discussion.
These calculations suggest that
DHQ (~(3~6)/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
K



D e K  partial reconstruction
D0
c
K
c
D0
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.
Ntag = Nunlike - N like
like sign pair subtraction
(Ntag is from semi-leptonic decay)
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%~).
Main uncertainty of ec and eb  •production ratios (D+/D0, Ds/D0 etc)
•contribution from NOT D(B) daughters
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5.2 ce/be via e-h correlation
Year5 p+p s=200GeV data set is used
comparison of data with simulation
theoretical uncertainty
is NOT included.
(0.5~5.0 GeV)
pt(e) 2~5GeV/c
c2 /ndf 58.4/45
@b/(b+c)=0.34
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5.3 ce/be via e-h correlation
Year5 p+p s=200GeV data set is used
(be)/(ce+be) as a function of electron pt
(b max) and (c min)
(b min) and (c min)
(b max) and (c max)
(b min) and (c max)
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Heavy quark measurement at PHENIX
K



direct measurement:
D0K+pp0
D0K+p-
D0
c
K
D0
p+
c
Meson
D±,D0
Mass
1869(1865) GeV
BR D0 --> K+p-
3.85 ± 0.10 %
BR D0 --> K+p-p0
14.1 ± 0.10 %
BR --> e+ +X
17.2(6.7) %
BR --> m+ +X
6.6 %
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6. Direct measurement of D0
D0K+p-p+ reconstruction
•
•
•
•
•
Year5 p+p s=200GeV data set is used
Observe 3s significant signal in pT D range 5 ~ 15 GeV/c
No clear signal is seen for pT D < 5 GeV/c
The signal is undetectably small for pT D > 15 GeV/c
Signal is fitted with parabola(B) + gaussian(S)
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6.2 Direct measurement of D0
D0K+p-p+ reconstruction
Momentum Dependence
•
•
•
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K+p- reconstruction with electron tag
Year5 p+p s=200GeV 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 Au+Au collisions
at √sNN=200GeV.
• be/(ce + be) has been studied in p+p collisions at
√s =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 p+p collisions at
√s =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 h → gg
In material: g → e+e- (Major contribution of photonic electron)
Dalitz decay of light neutral mesons
p0 h → g e+e- (Large contribution of photonic)
The other Dalitz decays are small contributions
Direct Photon (is estimated as very small contribution)
Non-photonic Electron
Heavy flavor electrons (the most of all non-photonic)
Weak Kaon decays
Ke3: K± → p0 e± e (< 3% of non-photonic in pT > 1.0 GeV/c)
Vector Meson Decays
w  f J → e+e- (< 2-3% of non-photonic in all pT.)
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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
Ne Electron yield
additional material
converter
(photon converter )
0.8% 0.4%
1.7%
With converter
Advantage is small systematic
error in low pT region
Photonic
W/O converter
Background in non-photonic
Dalitz : 0.8% X0 equivalent
radiation length
is subtracted by cocktail method
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p  L C
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Non-photonic
0
Material amounts: 0
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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)
X 1/Nnon-phot e
From real data
count
Electron pt 2~5GeV/c
Hadron pt 0.4~5.0GeV/c
edata
0.029 +- 0.003(stat)
+- 0.002(sys)
unlike pair
like pair
From simulation (PYTHIA and EvtGen)
charm
bottomproduction
production
charm
ec = 0.0364 +- 0.0034(sys)
bottom
eb = 0.0145 +- 0.0014(sys)
Electron pt 2~5GeV/c
Hadron pt 0.4~5.0GeV/c
unlike pair
like pair
(unlike-like)
/# of ele
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5. Result (electron Pt 2~3GeV/c)
comparison of data with simulation
theoretical uncertainty
is NOT included.
(0.5~5.0 GeV)
pt(e) 2~5GeV/c
c2 /ndf 58.4/45
@b/(b+c)=0.34
pt(e) 2~3GeV/c
c2 /ndf 34.3/22
@b/(b+c)=0.28
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5. Result (electron Pt 3~4GeV/c)
comparison of data with simulation
theoretical uncertainty
is NOT included.
(0.5~5.0 GeV)
pt(e) 2~5GeV/c
c2 /ndf 58.4/45
@b/(b+c)=0.34
pt(e) 2~3GeV/c
c2 /ndf 34.3/22
@b/(b+c)=0.28
pt(e) 3~4GeV/c
c2 /ndf 13.4/22
@b/(b+c)=0.66
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5. Result (electron Pt 4~5GeV/c)
comparison of data with simulation
theoretical uncertainty
is NOT included.
(0.5~5.0 GeV)
pt(e) 2~5GeV/c
c2 /ndf 58.4/45
@b/(b+c)=0.34
pt(e) 2~3GeV/c
c2 /ndf 34.3/22
@b/(b+c)=0.28
pt(e) 3~4GeV/c
c2 /ndf 13.4/22
@b/(b+c)=0.66
pt(e) 4~5GeV/c
c2 /ndf 21.9/22
@b/(b+c)=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 p+p 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 !
p+p 200 GeV
STAR QM2006
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Photon Converter
e
+
e-
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page4
Non-photonic electron v2
measurement
 Non photonic
electron
e
g .e v2 is given
nong .as;
e
dN
dN
dN


d
d
d
e
g .e
(1  RNP )v2  v2
nong .e
v2

RNP
v2e ; Inclusive electron v2
=> Measure
(1)
(2)
RNP = (Non-γ e) / (γ e)
=> Measure
v2 γ.e ; Photonic electron v2
 Cocktail method (simulation) stat. advantage
 Converter method (experimentally)
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page6
Inclusive electron v2
 inclusive electron v2 measured w.r.t reaction plane
 converter --- increase photonic electron
 photonic & non-photonic e v2 is different
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page7
Photonic e v2 determination
v2 (π0)
R = N X->e/ Nγe
pT<3 ; π (nucl-ex/0608033)
pT>3 ; π0 (PHENIX run4 prelim.)
decay
photonic e v2 (Cocktail)
 photonic electron v2
=> cocktail of photonic e v2
g .e
decay
2
2
v
  Rv
 good agreement
converter method
(experimentally determined)36