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Measurement of Heavy Quark production at RHIC-PHENIX

Yuhei Morino

CNS, University of Tokyo

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flow & energy loss ? insight into the property of the medium

1.Introduction

•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.

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.

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2.PHENIX experiment

• PHENIX central arm:– || < 0.35 = 2 x /2– p > 0.2 GeV/c

• Charged particle tracking analysis using DC and PC → p

• Electron identification– Ring Imaging Cherenkov de

tector (RICH) – Electro- Magnetic Calorimet

er (EMC) → energy E

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cc

0D

electron/muon from semileptonic decay

0D

K

+

K

direct measurement:DK, DK

Meson D±,D0

Mass 1869(1865) GeV

BR D0 --> K (3.85 ± 0.10) %

BR --> e +X D±: 17.2, D0: 6.7 %

3.Heavy quark measurement at PHENIX

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Upper limit of FONLL

PRL, 97, 252002 (2006)

• cc= 567 57(stat) ± 224(sys) b

• FONLL: Fixed Order plus Next to Leading Log pQCD

• Central value for data/FONLL predictions ~1.7 ( reasonable value)

Inclusive electron( conversion, daliz,etc 　　 and heavy quark )

Background subtraction

Non-photonic electron(charm and bottom)

3.2 Result of p+p at 3.2 Result of p+p at ssNNNN = 200 GeV = 200 GeV

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3.3 Result of Au+Au at 3.3 Result of Au+Au at ssNNNN = 200 GeV = 200 GeV

MB

p+p

0%~

~92%

Heavy flavor electroncompared to binary scaled p+p data (FONLL*1.71)

Clear high pT suppression in central collisions

PHENIX PRL98 173301 (2007)

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3.4 Nuclear Modification Factor: RAA

tpp

tAA

colltAA dpdN

dpdN

NpR

/

/1)(

large suppression!

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

PHENIX PRL98 173301 (2007) Djordjevic, PLB632 81 (2006)

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3.5 Non-photonic electron v2 Greco, Ko, Rapp: PLB 595 (2004) 202

data suggests non-zero charm v2

charm is strongly coupled to the matter.

pQCD fail [PRB637,362]

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3.6 comparison with models.

• pQCD radiative E-loss with 10-fold upscaled transport coeff.

• elastic pQCD + D resonances + coalescence

• 2-6 upscaled pQCD elastic

various models exist.

These calculations suggest that DHQ (~(3~6)/2T..near quantum bound) are required to reproduce the data.

PLB649(2007)139

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

be RAA

ce RAAbehavior of bottom differ from charm c/b separation is necessaryfor further discussion.

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4. B contribution to non-photonic electron

• FONLL: Fixed Order plus Next to Leading Log pQCD calculation

Large uncertainty on c/b crossing 3 to 9 GeV/c

Experimental determination of ce/be is one of most important next steps

FONLL:

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cc

0D

electron/muon from semileptonic decay

0D

K

+

K

Heavy quark measurement at PHENIX

D e K partial reconstruction

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5 ce/be via e-h correlation

Ntag = Nunlike - N like

unlike sign e-h pairs contain large background from photonic electrons.like sign pair subtraction (Ntag is from semi-leptonic decay)

From real data analysisNc(b)e is number of electronsfrom charm (bottom)Nc(b)tag is Ntag from charm (bottom)

From simulation (PYTHIA and EvtGen)

data can be written by only charm and bottom component

The tagging efficiency is determined only decay kinematics and the production ratio of D(B)hadrons to the first order(85%~).

Main uncertainty of c and b •production ratios (D+/D0, Ds/D0 etc)•contribution from NOT D(B) daughters

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theoretical uncertaintyis NOT included.

comparison of data with simulation (0.5~5.0 GeV)

pt(e) 2~5GeV/c2 /ndf 58.4/45 @b/(b+c)=0.34

5.2 ce/be via e-h correlationYear5 p+p s=200GeV data set is used

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(be)/(ce+be) as a function of electron pt

(b max) and (c min)

(b min) and (c min)

(b min) and (c max)

(b max) and (c max)

5.3 ce/be via e-h correlationYear5 p+p s=200GeV data set is used

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cc

0D

0D

K

+

K direct measurement:

D0K+D0K+-

Heavy quark measurement at PHENIX

Meson D±,D0

Mass 1869(1865) GeV

BR D0 --> K+- 3.85 ± 0.10 %

BR D0 --> K+-0 14.1 ± 0.10 %

BR --> e+ +X 17.2(6.7) %

BR --> ++X 6.6 %

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6. Direct measurement of D0

• Year5 p+p s=200GeV data set is used• Observe 3 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)

D0K+-+ reconstruction

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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 r

ange

6.2 Direct measurement of D0

D0K+-+ reconstruction

Analysis to determine invariant cross section is on going.

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6.3 Direct measurement of D0

D0K+- reconstruction with electron tag

tag

reconstruct

real eventmixing event

back ground subtracted

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

Year5 p+p s=200GeV data set is used

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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.• be/(ce + be) 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 D0K+ - 0 and D0K+ - 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

Photon Conversion

Main photon source: → In material: → e+e- (Major contribution of photonic electron)

Dalitz decay of light neutral mesons→ e+e- (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± → e± e (< 3% of non-photonic in pT > 1.0 GeV/c) Vector Meson Decays

J → e+e-(< 2-3% of non-photonic in all pT.)

Photonic Electron

Non-photonic Electron

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Most sources of backgroundhave 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.

Background Subtraction: Cocktail Method

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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

Ne Electron yield

Material amounts:

0

0.4% 1.7%

Dalitz : 0.8% X0 equivalent radiation length

0

With converter

W/O converter

0.8%

Non-photonic

Photonic

converter

CLp 9

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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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charm productionbottom productioncharm c = 0.0364 +- 0.0034(sys)bottomb = 0.0145 +- 0.0014(sys)

4. Analysis(2)

unlike pairlike pair

From real data

Electron pt 2~5GeV/cHadron pt 0.4~5.0GeV/c

countX 1/Nnon-phot e data

0.029 +- 0.003(stat) +- 0.002(sys)

From simulation (PYTHIA and EvtGen)

Electron pt 2~5GeV/cHadron pt 0.4~5.0GeV/c

unlike pairlike pair

(unlike-like)/# of ele

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5. Result (electron Pt 2~3GeV/c)theoretical uncertaintyis NOT included.comparison of data with simulation

(0.5~5.0 GeV)

pt(e) 2~5GeV/c2 /ndf 58.4/45 @b/(b+c)=0.34

pt(e) 2~3GeV/c2 /ndf 34.3/22 @b/(b+c)=0.28

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5. Result (electron Pt 3~4GeV/c)theoretical uncertaintyis NOT included.comparison of data with simulation

(0.5~5.0 GeV)

pt(e) 2~5GeV/c2 /ndf 58.4/45 @b/(b+c)=0.34

pt(e) 2~3GeV/c2 /ndf 34.3/22 @b/(b+c)=0.28

pt(e) 3~4GeV/c2 /ndf 13.4/22 @b/(b+c)=0.66

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theoretical uncertaintyis NOT included.comparison of data with simulation

(0.5~5.0 GeV)

pt(e) 2~5GeV/c2 /ndf 58.4/45 @b/(b+c)=0.34

pt(e) 2~3GeV/c2 /ndf 34.3/22 @b/(b+c)=0.28

pt(e) 3~4GeV/c2 /ndf 13.4/22 @b/(b+c)=0.66

pt(e) 4~5GeV/c2 /ndf 21.9/22 @b/(b+c)=0.75

5. Result (electron Pt 4~5GeV/c)

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6.DiscussionCollisional dissociation in hot and dense matter?

Input be/ce

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

suppression of non-photonic electron is not so strong asprediction 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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p+p 200 GeV

• Fit e-h correlation with PYTHIA D and B

• Data shows non-zero

B contribution

STAR QM2006

Bottom !

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Photon Converter

e+

e-

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Non-photonic electron v2 measurement

Non photonic electron v2 is given as;　

v2 γ.e ; Photonic electron v2

Cocktail method (simulation) stat. advantage Converter method (experimentally)

v2e ; Inclusive electron v2

=>　Measure RNP = (Non-γ e) / (γ e)=> Measure

NP

eeNPenon

enonee

R

vvRv

d

dN

d

dN

d

dN

.22.

2

..

)1(

page4

(1)

(2)

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Inclusive electron v2

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

page6

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Photonic e v2 determination

decaye vRv 2.

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good agreement converter method (experimentally determined)

photonic electron v2

　 => cocktail of photonic e v2

page7

R = N X->e/ Nγe

photonic e v2 (Cocktail)

decay

v2 (π0)

pT<3 ; π (nucl-ex/0608033)pT>3 ; π0 (PHENIX run4 prelim.)