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Measurement of charm and bottom production in pp collisions

at √s = 200 GeV at RHIC-PHENIX

Yuhei Morino for the PHENIX collaborationCNS, University of Tokyo

JSPS

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1.Introduction

Observation via lepton measurement•Large energy loss•Large V2strongly interacting matter for charm!

Behavior of heavy quarks in hot&dense matter

charm and bottom are not separated.

Need to separate charm/bottom to get more information.

next open question•bottom flow?•bottom energy loss?

RUN4RUN7

A.Dion[poster]

min.bias

Phys. Rev. Lett. 98, 172301 (2007)

b contribution?

@hot&dense matter

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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.This talk will show the latest result of measurement of c,bin p+p collisions at mid-rapidityAu+Au results were reported at D.Hornback’s talk

Phys.Rev.Lett 95 122001

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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) %

•direct ID (invariant mass)•large combinatorial background

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

c c

0D

0D-

K

direct measurement

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2 Measurement of non-photonic electron measurementInclusive electron

( conversion, Dalitz,etc and heavy quark )

Background subtraction•cocktail method•converter method

Non-photonic electron(charm and bottom). c c

Semileptonic decay0D

Fragmentation

D e K partial reconstruction

be/(ce+be)?PRL, 97, 252002 (2006)

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

K e-

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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

•first result of b fraction measurement at PHENIX•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))

data/FONLL ~2 reasonable value

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pt extrapolation of be spectra by pQCD

First measurement of bottom cross section at mid-rapidity in p+p collisions at PHENIX.rapidity extrapolation by NLO pQCD (|y|<0.35y integrated)

bb(data)/bb(FONLL)~2

cross section of bottom

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3 Heavy quark measurement via di-electron

c c

0D

0D

e

K

e-

e+

heavy quark is dominantsource @mee >1.1GeV

arXiv:0802.0050 A.Toia[talk]e+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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4 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%)

Clear peak of D0 （ 5<pt<15GeV/c) meson observed in D0K- + 0 decay channel

S.Butsyk[poster]

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D0K-+ reconstruction with electron tag

tag

reconstruct

electron tag reduce combinatorial background

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

P.Shukla [poster]

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5 Summary and Outlook• be/(ce + be) has been studied in p+p collisions at √s =200GeV via e-h c

orrelation. Cross section of bottom was obtained from electron spectra and be ratio.

・ Consistent with FONLL calculation (data/fonll ~ 2) ・ This is baseline measurement for understanding heavy quark energy l

oss and v2 observed in Au+Au collisions and further discussion on heavy quark energy loss will be done.

• Cross sections of charm and bottom were obtained from di-electron in p+p collisions at √s =200GeV.

• Clear peak of D0 meson observed in p+p collisions at √s =200GeV in D0->K+ - 0 and D0->K+ - channels.

・ Analysis to determine cross section is on going.

• Silicon Vertex Tracker will be installed for more precise study.

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back up

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Electron Signal and Background

Conversion of photons in material 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] … Background

[Non-photonic electron] … Signal and minor background

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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 was installed)Advantage is small systematic error in low pT regionBackground in non-photonic issubtracted by cocktail method

Photon Converter (Brass: 1.7% X0)

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

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Consistency Check of Two MethodsAccepted by PRL (hep-ex/0609010)

Accepted by PRL (hep-ex/0609010)

Both methods were always checked each other

Ex. Run-5 p+p in left

Left top figure shows Converter/Cocktail ratio of photonic electrons

Left bottom figure shows non-photon/photonic ratio

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• 2.25pb-1 of triggered p+p data as reference

• 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

π0

π0

e+

e-

e+

e-

γ

γ

π0

e-

γ

e+

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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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Acceptance filter and symmetrical fiducial cutphi0phi

phi*

Phi … detected phi of charged trackPhi*… expected phi when charged track has an opposite charge. (swapped phi around phi0)

Symmetrical fiducial cut

pt

phi0

Positive charged track negative charged track

symmetrical

Fiducial cut is also applied for phi*.(symmetrical fiducial cut)This cut will make phase space symmetrical.

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

4. Analysis(RUN5)

unlike pairlike pair

From real dataElectron 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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Electron pt 2~3 GeV/c Electron pt 3~4 GeV/c

Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

Unlike pairLike pair

Electron-hadron invariant mass(RUN5)Mass of hadron is assigned 494MeV, hadron 0.4 < pt <5 GeV/c

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Estimation of systematic error for signal counting

Electron pt 2~5 GeV/c

Mixing unlike pairMixing like pair

real unlike / real likemixing unlike/ mixing like

mixing unlike / mixing like ~=1, there are no effect of phase space

mixing unlike/ mixing like

RMS is 2%.I will assign this 2% as systematicerr about signal counting.

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unlike/like ratios Vs invariant massElectron pt 2~3 GeV/c Electron pt 3~4 GeV/c

Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

Real Mixing event

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Electron-hadron (unlike – like) invariant mass(RUN5)

Electron pt 2~3 GeV/c Electron pt 3~4 GeV/c

Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

0.5 < invariant mass <1.9 GeV pairs are counted as signals.

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Remaining electron – electron pair rejection(RUN5)Electron veto cut for hadron (n0<0) cannot all electron due to RICH acceptance.pair mass (mass of hadron is assigned 0.511MeV)>0.08GeV cut was used fore-e pairs rejection. But there are remaing electron pairs

Electron(2<pt<5) electron (0.4<pt<5 , n0>=2,e/p>0.7)

Electron(2<pt<5) hadron (0.4<pt<5,n0<0), mass is assigned 0.511Mev

Rejected by pair cut

Unlike pairLike pair

Unlike pairLike pair

Mass of associate particle is assigned 494MeV

remaing e-e pairs are estimated by invariant mass distributionwhen mass of associated electron is 0.494Mev.Normalization factor is (# of e-h pair in invariant mass <0.08) / (# of e-e pair in invariant mass <0.08)

e –h pairEstimated remaining e-e pair

Estimated e-e pairs are subtracted.Systematic error of this subtraction is estimatedby statistics of (# of e-h pair in invariant mass <0.08) / (# of e-e pair in invariant mass <0.08)

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spectra of FONLL&PTYHIA(1.5<kt<10GeV/c)4.21 +- 0.4

PYTHIA & EvtGen combination::0.88

PDG value & changing B hadron ratio::10+-1%

PYTHIA & HVQMNR(NLO QCD)3.44+-0.25

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Electron-hadron (unlike – like) invariant mass(RUN5)after remaining e-e pair rejection

Electron pt 2~3 GeV/c Electron pt 3~4 GeV/c

Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

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High Pt extensioneID … tight cut hadron background was estimated from e/p distribution

the effect of h-h correlationhadron iD … standard eID cut +prob<0.01 +0.6<e/p<0.8 99% hadron

hadron :: 0.087+- 0.043(50% systematic error)

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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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c c

0D

K

D*

EvtGen products

PYTHIA products

EvtGen and PYTHIA products

string

charm (bottom) gluon

string

D*

gamma

D0

e+ K- nu

pi0

gamma ………

EvtGen only

EvtGen+PYTHIA

Fast monte carlo calculation for EvtGen ony and EvtGen+PYTHIA electron pt 2~5GeV/c EvtGen+PYTHIA … c 0.0342 EvtGen only …c0.0301

~15% of c are from PYTHIA. This part may be changed by PYTHIA fragmentation,etcI assign PYTHIA 20% systematic error. This error corresponds 3% error for c

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photonic electron unlike/like

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Hadron contamination (pt>5 GeV/c)

e/p

count5~6 GeV/c 6~7 GeV/c 7~8 GeV/c

8~9 GeV/c 9~10 GeV/c

tight eid cut (normal && n1>4 &&prob>0.1)estimated hadron (at previous page)

electron peak is clearly seen at pt<9GeV/c

fit estimated hadron distribution(back ground)Fix Fit e/p distribution at tight eid cut

hadron contamination (e/p>0.9) was estimated these fit functions.

3% 5% 11%

12% 17%