# Presentation: 474469

## Measurement of charm and bottom production in pp collisions at √s = 200 GeV at RHIC-PHENIX 

- Yuhei Morino for the PHENIX collaboration
- CNS, University of Tokyo
- JSPS

## 1.Introduction

**1.Introduction**

- Observation via lepton measurement
- Large energy loss
- Large V2
- strongly 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?

- _[Phys. Rev. ](http://link.aps.org/abstract/PRL/v98/e172301)__[Lett](http://link.aps.org/abstract/PRL/v98/e172301)__[. 98, ](http://link.aps.org/abstract/PRL/v98/e172301)__[172301](http://link.aps.org/abstract/PRL/v98/e172301)__[ (2007)](http://link.aps.org/abstract/PRL/v98/e172301)__[ ](http://link.aps.org/abstract/PRL/v98/e172301)_

**b contribution?**

**@hot&dense matter**

## b contribution to non-photonic electron

**b contribution to non-photonic electron**

** ****FONLL: ****F**ixed **O**rder plus **N**ext to **L**eading **L**og pQCD calculation
**  ****Large uncertainty**** on c/b crossing 3 to 9 GeV/c**

- Measurement of be/ce is key issue.
- This talk will show the latest result of measurement of c,b
- in p+p collisions at mid-rapidity
- Au+Au results were reported at D.Hornback’s talk

- Phys.Rev.Lett 95 122001

## Heavy quark measurement at PHENIX 

- direct ID (invariant mass)
- large combinatorial background

**lepton from semileptonic decay**
- large branching ratio
- c and b mixture

******-**

- direct measurement

********

## 2 Measurement of non-photonic electron 

**2 Measurement of non-photonic electron **

_***measurement***_

- Inclusive electron
- ( conversion, Dalitz,etc and heavy quark )

- Background subtraction
- cocktail method
- converter method

- Non-photonic electron
- (charm and bottom)

- .

-      Semileptonic decay

- be/(ce+be)?

**PRL, 97, 252002 (2006)**

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

- e-

## {

- Ntag  = Nunlike - N like

- D0e+ K-(NO PID) reconstruction

- From data

- From simulation (PYTHIA and EvtGen)

**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%)

## reconstruction signal and simulation

**reconstruction signal and simulation**

## bottom fraction in non-photonic electron

**bottom fraction in non-photonic electron**

- first result of  b fraction measurement at PHENIX
- The result is consistent with FONLL

## electron spectra from charm and bottom

- charm

- bottom

**PRL, 97, 252002 (2006)**

- be = (non-photonic) X (be/(ce+be))

- data/FONLL ~2 reasonable value

## cross section of bottom

- pt extrapolation of be spectra by pQCD

- First measurement of bottom cross section at mid-rapidity
- in p+p collisions at PHENIX.
- rapidity extrapolation by NLO pQCD (|y|<0.35y integrated)
- bb(data)/bb(FONLL)~2

**cross section of bottom**

## 3 Heavy quark measurement via di-electron

- heavy quark is dominant
- source @mee >1.1GeV

- arXiv:0802.0050

- A.Toia[talk]

- e+e- pair

##   Di-electron from heavy quark

**  ****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,be agree!

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

## total cross section of charm and bottom

**total cross section of charm and bottom**

- √s dependence of cross section with NLO pQCD
- agrees with data

## 4 Direct measurement  of D meson

## D0K-+0 reconstruction

- large branching ratio(14.1%)

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

- S.Butsyk[poster]

## D0K-+ reconstruction with electron tag

**D****0********K****-********+ ****reconstruction with electron tag**

- electron tag reduce combinatorial background

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

- P.Shukla [poster]

## 5 Summary and Outlook

- be/(ce + be) has been studied in p+p  collisions at  √s =200GeV via e-h correlation. Cross section of bottom was obtained from electron spectra and be ratio.
-         ・Consistent with FONLL calculation (data/fonll ~ 2)
-         ・This is baseline measurement for understanding heavy quark energy       loss 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.

## back up

## 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**
**	****K****e3****: K****±**** → ************ e****±**** ********e**** (< 3% of non-photonic in p****T**** > 1.0 GeV/c)**
**Vector Meson Decays**
**	********J******** → e****+****e****-********(< 2-3% of non-photonic ****in all p****T****.****)**

**[Photonic electron] ... Background**

**[Non-photonic electron] ... Signal and minor background**

## 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.**

**Background Subtraction: Cocktail Method**

## Background Subtraction: Converter Method

**We know precise radiation length (X****0****) 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 p****T ****region**
**Background in non-photonic is**
**subtracted by cocktail method**

**Photon Converter (Brass: 1.7% X****0****)**

## Consistency Check of Two Methods

**Accepted 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**

## 
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

- 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

## 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 procedure explained in the next slide

## 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

## ce, be spectra 

- ce, be spectra

- # of non-photnic electron in b/(b+c)  PPG65 spectra
- sys error of # of non-photnic electron 100%correlation sys error of PPG65
- enlarge sys error of bottom

- non-photonic
- electron
- (total>b)

- 90% C.L

## Acceptance filter and symmetrical fiducial cut

- Symmetrical fiducial cut

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

## 4. Analysis(RUN5)

- charm
- c = 0.0364 +- 0.0034(sys)
- bottom
- b = 0.0145 +- 0.0014(sys)

- From simulation (PYTHIA and EvtGen)

- Electron pt  2~5GeV/c
- Hadron pt 0.4~5.0GeV/c

- unlike pair
- like pair

**(unlike-like)**
**/# of ele**

## Electron-hadron 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

- Unlike pair
- Like pair

- Mass of hadron is assigned 494MeV, hadron 0.4 < pt <5 GeV/c

## Estimation of systematic error for signal counting 

- Electron pt 2~5 GeV/c

- Mixing unlike pair
- Mixing like pair

- real unlike / real like
- mixing 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 systematic
- err about signal counting.

## unlike/like ratios Vs invariant mass

- Electron 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

## 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.

## 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 for
- e-e pairs rejection. But there are remaing electron pairs

- Unlike pair
- Like pair

- Unlike pair
- Like pair

- Mass of associate particle
- is assigned 494MeV

- remaing e-e pairs are estimated by invariant mass distribution
- when 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 pair
- Estimated remaining e-e pair

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

## spectra of FONLL&PTYHIA(1.5<kt<10GeV/c)

**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**

## 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

## High Pt extension

- eID ... tight cut
- hadron background was estimated from e/p distribution

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

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

## EvtGen 

**EvtGen **

## 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 ...c0.0301

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

## photonic electron unlike/like

## Hadron contamination (pt>5 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%