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Measurement of charm and bottom production in RHIC-PHENIX

Yuhei Morino for the PHENIX collaborationCNS, University of Tokyo

JSPS DC fellow

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1.Introduction

•Heavy quarks (charm and bottom) are produced at only initial stage good probe for studying property of the medium.•p+p collisions base line study, pQCD test.•Au+Au collisions energy loss, flow? @ hot and dense matter

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.

Freeze-out

Pre-equilibrium

QGP

Hadron gas

Hadronization

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Heavy quark measurement at PHENIX

•direct ID (invariant mass)•large combinatorial background

lepton from semileptonic decay•large branching ratio•c and b mixture

c c

0D0D-

K

direct measurement

(single&di) lepton measurement is powerful tool for the study of heavy quarkp+p ~ Au+Au collisions

IN ADDITIONAt p+p (d+Au) collisions,direct measurement, e-h, e-correlationcan be used.important base line study.

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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

RNXP detector was installed at RUN7improve determination of reaction plane

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

Background subtraction

Non-photonic electron(charm and bottom)

2 Measurement of non-photonic electron

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

Converter method

S/N>1@pt>2GeV/c

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Phys. Rev. Lett 97,252002 (2006)

non-photonic electron (p+p@200GeV)

• Single electrons from heavy flavor (charm/bottom) decay are measured and compared with pQCD theory

• FONLL pQCD calculation agree with the data

(Fixed Order plus Next to Leading Log pQCD)

• cc= 567 57(stat) ± 224(sys) b

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FONLL:

FONLL c/(b+c)FONLL c/(b+c) FONLL b/(b+c)

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

Measurement of be/ce is key issue.

Phys.Rev.Lett 95 122001

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decay component (~85%)kinematics

Ntag = Nunlike - N likeD0e+ K-(NO PID) reconstruction

From data

From simulation (PYTHIA and EvtGen)

Main uncertainty of c and b •production ratios (D+/D0, Ds/D0 etc)

c,b separation in non-photonic electron

background subtraction(unlike-like)•photonic component•jet component

tagging efficiency when trigger electron is detected,conditional probability of associate hadron detectionin PHENIX acc 　

{ jet component (~15%)

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counttagging efficiency (c,b,data)

reconstruction signal and simulation

2 /ndf 21.2/22 @b/(b+c)=0.26(obtained value)(0.5~5.0GeV)2 /ndf 28.5/22 @b/(b+c)=0.42(obtained value)(0.5~5.0GeV)2 /ndf 18.7/22 @b/(b+c)=0.56(obtained value)(0.5~5.0GeV)

•tag efficiency of charm increases as electron pt•tag efficiency of data gets near bottom

c

b

data

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bottom fraction in non-photonic electron

•The result is consistent with FONLL

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electron spectra from charm and bottom

charm

bottom

PRL, 97, 252002 (2006)

be = (non-photonic) X (be/(ce+be))

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• Material conversion pairs removed by analysis cut

• Combinatorial background removed by mixed events

• additional correlated background:– cross pairs from decays with

four electrons in the final state– particles in same jet (low

mass)– or back-to-back jet (high mass)

• well understood from MC

p+p at √s = 200GeV

arXiv:0802.0050

3 Measurement of di-electron(p+p@200GeV)

arXiv:0802.0050

p+p at √s = 200GeV

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Heavy quark measurement via di-electron

c c

0D

0D

e

K

e-

e+

heavy quark is dominantsource @mee >1.1GeV

arXiv:0802.0050e+e- pair

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Di-electron from heavy quark

c dominant

b dominant

cocktail calculations are subtracted from data

After Drell-Yan subtracted,fit (a*charm+b*bottom)to the data.

charm and bottom cross sections from e+e- and c,be agree!

bottom, DY,subtraction charm signal !!mass extrapolation (pQCD)rapidity extrapolation (pQCD)

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total cross section of charm and bottom

√s dependence of cross section with NLO pQCDagrees with data

total cross section of bottom

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Summary of p+p@200GeV results• non-photonic electron spectra was obtained in p+p@200GeV.

– data/FONLL~1.7• be/(ce + be) has been studied in p+p collisions at √s =200GeV via

e-h correlation. Cross section of bottom was obtained from electron spectra and be ratio.– b->e/c->e ~1 @ pt~3GeV/c

• Cross sections of charm and bottom were obtained from di-electron in p+p

collisions at √s =200GeV.– charm and bottom cross sections from e+e- and c,be agree

On going issues in p+p@200GeV • Direct reconstruction in D0K-+ 0 and D0K- + channels. - clear peak has been obtained.

• e-correlation

D0K- + 0 decay channelD0K-+ with electron tagtag

reconstruct

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4Measurement of di-electron(Au+Au@200GeV)

c ce e dominant

arXiv:0706.3034

Cocktail agrees with data points@1.2<Mee<2.8.

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MB

p+p

0%~

~92%

５ non-photonic electron (Au+Au@200GeV)

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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Nuclear Modification Factor: RAA

tpp

tAA

colltAA dpdN

dpdNN

pR//1)(

large suppression athigh pt

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

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

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Adil & Vitev, PLB 649(2007)139

Comparison with models

• pQCD radiative E-loss with large transport coeff.(BDMPS)

• elastic pQCD + D resonances + coalescence

• upscaled pQCD elastic

radiative & collisional E-lossmodels.

alternative approaches•collisional dissociation of heavy meson•heavy baryon enhancement

be/ce>~1 @ pt>~3GeV/cbottom may also lose large energy in (s)QGP

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V2 of non-photonic electron

PRELIMINARYRun-4

Run-7

Rapp & van Hees, PRC 71, 034907 (2005)

minimum-biaslarge v2 has been observed charm flow

new result suggest significantv2 at high ptbottom also flow?

To reproduce suppression pattern & v2,

small τ and/or DHQ are required(Rapp&van Hees, Moore and Teaney)/s ~(1.3-2)/4 quantum limit

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6 Summary• di-electron spectra was obtained in Au+Au@200GeV

• non-photonic electron spectra was obtained in Au+Au@200GeV– large suppression pattern@high pt and large v2 was observed.

charm lose large energy loss and flow in (s)QGP. & be/ce >~ 1 @ pt>~3GeV/c (from p+p data) bottom lose large energy loss and flow in (s)QGP?

• Model comparison suggests– smallτ and/or DHQ are required

– η/s is very small, near quantum bound.

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Outlook• more high pt v2 ?• electron –hadron correlation at Au+Au@200GeV ?• RAA dependence on path length ?• Silicon vertex detector

PRELIMINARYRun-4Run-7

Rapp & van Hees, PRC 71, 034907 (2005)

minimum-bias

?

0 – 20%: 3 < pTtrig < 6 GeV/c & 0.15 < pTasso < 1 GeV/c

STAR Preliminary

0RAA dependence on density-weighted average path length

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back up

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4Measurement of di-electron(Au+Au@200GeV)

c ce e dominant

Yield(1.2<mee<2.8GeV)/Ncoll

•No significant centrality dependence•consistent with PYTHIA & random cc scenarios

arXiv:0706.3034

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Direct measurement of D meson

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) %

•direct ID(peak)•large combinatorial background

c c

0D

0D

-

Kdirect measurement:DK, DK

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D0K-+0 reconstructionlarge branching ratio(14.1%) S.Butsyk[poster]

D0K- + 0 decay channel

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electron tag reduce combinatorial background

•observe D0 peak•cross section of D is coming up

P.Shukla [poster]

D0K-+ with electron tagtag

reconstruct

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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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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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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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Method I• Tune cocktail to PHENIX measured hadrons• Subtract cocktail• Extract cross section in multi steps as in ppg065

– A. dsigma_ee/dy(1.1<Mee<2.5; in ideal PHENIX acceptance) This is what directly measured. Only systematic error in the data and Statistical data present.

– A1. Extrapolate to 0<M<5 GeV; However, since ds/dy(1.1<M<2.5) is a very tiny fraction of dsigma/dy(0<M), I would rather not mention about it.

– B. dsimga_ee/dy(1.1<Mee<2.5; |ye|<0.35)This is when two arm acceptance of PHENIX is corrected. Since the two arm nature is corrected, this is something a theorist can easily calculate.(now acceptance error is involved)

– C. dsimga/dy of ccbar (now PYTHIA error is involved: kt, pdf’s and branching ratio because we go from electrons to charm)

– D. sigma(ccbar) total (now add error for rapidity distribution)• In the paper we mention only A., C. and D. for simplicity• A. is calculated from the data, C. and D. are derived in the procedur

e explained in the next slide

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Method II• Tune cocktail to PHENIX measured hadrons• Subtract cocktail• Fit p0*charm + p1*bottom + drell yan

– Charm cross section = 567 b (ppg065)– Beauty cross section = 3.77 b (Claus Jaroceck and commonly used in single electron

analysis)– Drell Yan = 0.040 b and scaled to NLO calculations from Werner Vogelsang

• DY (from PYTHIA) + p0*charm +p1*bottom–     p0           9.13960e-01 ± 8.24258e-02 – p1           1.06418e+00 ± 7.13970e-01

• DY (scaling Pythia to Werner’s calculations for M>4GeV) + p0*charm +p1*bottomQ/2

–     p0           9.08741e-01 ± 8.25467e-02 –     p1           1.14892e+00 ± 7.17499e-01 Q–     p0           8.97103e-01 ± 8.25275e-02 –     p1           1.24826e+00 ± 7.17928e-01 Q*2–     p0           9.09590e-01 ± 8.25467e-02 –     p1           1.13538e+00 ± 7.17499e-01

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ce, be spectra # of non-photnic electron in b/(b+c) PPG65 spectrasys error of # of non-photnic electron 100%correlation sys error of PPG65enlarge sys error of bottom

50%

non-photonic electron(total>b)

90% C.L

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EvtGen

PYTHIA EvtGen PISA Produce D (B) products Decay D (B) products Simulate detector response

b

bbar

B0

Bs+

b

bbar

B0

Bs+

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Cross subtraction

Data: likeMonte Carlo:Cross LikeCross Unlike

ForegroundBackgroundSubtracted

• 0*

e+e- e+e-

External conversionremoved with V cut

X

UnlikeCross LikeCross Unlike4-body

Yield in 4

Yield in acceptance

Add all contributions from 0, , 30