# Presentation: 843830

## Open Heavy Flavor Production in pp, dAu and AuAu Collisions at √sNN =200 GeV 

**Xiaorong Wang **
**for PHENIX collaboration**
**New Mexico State University**

## Outline

**Physics motivation **
**Experimental techniques **
**“****Prompt muons” and “Non-photonic” electron results from pp and dAu collisions**
**Nuclear modification factor R****dAu**
**“****Non-photonic” electron results from Au+Au collisions**
**Nuclear modification factor R****AA**
**Electron elliptic flow **
**Summary & outlook**

## Physics Motivation:

**pp collisions: **
- Provide the critical test for pQCD calculations of heavy-quark production
**dAu collisions: probe cold nuclear medium effects **
- Gluon saturation/CGC  at forward rapidity (small x)
- Coherent multiple scattering and XB rescaling
**AuAu collisions:** **probe hot and high density matter effects**
- “dead cone” effect:  charm quark small energy loss (in vacuum)
-  Heavy quark energy loss in medium
- suppression pattern: Little for B, moderate for c, and large for light q.
- 	  RAA(e) > 0.5

**Notes:**
Open charm measurement is one of the most direct probes of the early stage evolution of the QGP produced in relativistic heavy-ion collisions 

Because of the large quark masses, charm and bottom production can be treated by perturbative QCD even at small momenta without being significantly affected by additional soft process

dAu collision at RHIC as a compare experiment create the cold nuclear medium. To study the cold nuclear medium effect is a important baseline to understand the hot dense matter created in AuAu collision.

We know that If there’s no modification of the initial parton distribution or the final fragmentation, particle production will be scaled with the number of binary collisions
Gluon satuation and CGC ( Color Glass Condensate )  predict There will be modification of the initial parton distribution, and the scaling will be modified as a function of rapidity. 
		D. Kharzeev et al, Phys. Lett. B599 (2004) 23-31Iven and Qiu’s theory model, taking into account the Coherent multiple scattering and xb(pt/1\sqrt(s) rescaling aslo predict the suppression in forward rapidity. 

Au-Au collision creat hot and high desity medium.
By comparison of  the particle production in dAu and AuAu collision, we can understand the  hot density medium effects only created in AuAu collision.    

In the other hand, some theory models also have been develped to understand the hot dense matter effect in AuAu collisions at RHIC energy.
Here I list two of them, one is so called””, this model proposed the in the vacuum, charm quark will have small energy loss due to the big mass.

Also recently caculation of heavy quark energy loss in medium caculated the suppression pattern and Raa

Systemtically study open heavy flavor production in different collision system, in wider kinamatic ranges will help us to understand all these interesting uncleared physics questions.

## PHENIX detector 

- Electrons: central arms
- |η| < 0.35, p > 0.2 GeV/c

- Muons: muon arms
- 1.2 < |η| < 2.4, p > 2 GeV/c

- K+

- -

- e+

**D*****0**

********

**Notes:**
How does phenix detector measure open heavy flavor? 
Open charm and bottom can be measured through semi-leptons decay channel.
This  is the open charm semi-lepton decay diagram and also example of the inelastic decay channels to e and muon 

PHENIX detector is Optimized for lepton measurements. Central arm can measure p>0.2 GeV electrons in eta .., two muon arms can meaure

Challenge part of  this measurement is  background subtraction. 
Next two slides, I will briefly descript the analysis techniques used to subtract the background  of the non-photonic e and prompt muons separately. 

Br D+- (D0) 17.2(6.7) % (e and muon)

## Two complimentary analysis techniques for signal extraction
“Cocktail subtraction” 
“Converter subtraction” 
Both analyses clearly show an excess “non-photonic” electron signal attributed to heavy flavor decays 

- “Cocktail subtraction”
- “Converter subtraction”
- Both analyses clearly show an excess “non-photonic” electron signal attributed to heavy flavor decays

**Analysis Techniques: (non-photonic e)**

- Run04: X=0.4%

- Run02: X=1.3%

- Signal/Background

- S/B > 1 for pT > 1 GeV/c

**Notes:**
calculation of “photonic” electron background from all known sources 
extraction of “photonic” electron background by special run with additional converter

The right hand side plot shows the cocktail subtraction for AuAu at 200 GeV.

## Prompt μ background subtraction
Punch-through hadrons: 
Data driven method to Estimate  attenuation
Decay muons: Vertex distribution analysis

- Punch-through hadrons:
- Data driven method to Estimate  attenuation
- Decay muons: Vertex distribution analysis

**Analysis Techniques: (prompt muon)**

- Muon
- detector

**Notes:**
The main background sources for prompt muon in muon arms are Punch through hadrons and muons from k pi decay. 

For punch through: 

For decay muons: let’s take a close look at the muon detector. The collision can be happened with +-40cm anywhere, so if the collision happens close to one of the muon arm(south), it will travel long distance to another arm, so it will have more decay muons goes to north arm. The vertex distribution will shows strong vertex dependence.

Now we can look at our measurement for pp and 

## p+p at √s = 200 GeV: Final Non-photonic e & Preliminary Prompt  Invariant Cross section

***Muon spectra and electron spectra are similar ***
***             ******over the observed p******T****** range...***

**Notes:**
So far, PHENIX measured production of non-photonic e with central arms and prompt  with muon arms in p+p, d+Au collisions at 200 GeV

## Comparison to Theory

- FONLL: Fixed Order next-to-leading order terms and Next-to-Leading-Log large pT resummation.

***FONLL and PYTHIA calculation is under predicted PHENIX electron data. The discrepancy is even larger at forward rapidity, possibly due to the rapidity dependence of cross section.***

**Notes:**
PYTHIA 6.205 parameters, tuned to describe existing s < 63 GeV p+N world data 
( PDF – CTEQ5L, mC = 1.25 GeV, mB = 4.1 GeV, 
<kT> = 1.5 GeV, K = 3.5 )

## d+Au at √sNN = 200 GeV: Non-photonic e±  

***“***_***binary scaling” at mid-rapidity***_

**Notes:**
We observe “binary scaling” in non-photonic e production at midrapidity for d+Au collisions at √sNN = 200 GeV, which is consistent with the point-like interaction for charm production.

## dAu at √s = 200 GeV: Prompt  at Forward & Backward

**Cold nuclear medium effects are significant:**
**Intrinsic  Shadowing;      **
**coherent multiple scattering; **
**3)  initial state energy loss; ...  **

**Suppression in forward rapidity;**** ****Enhancement in backward rapidity;**
**Different from central rapidity result!!**

**Au going**
**d going**

**Notes:**
In order to fully understand the cold nuclear medium effects we have to explore the wider kinematics ranges. 

## AuAu at √s = 200 GeV: Non-photonic e

- Non-photonic :Inclusive
- Curves:
- Binary scaled p+p reference
- Clear high pT suppression developing towards central collisions

## Nuclear Modification Factor RAA

**Nuclear Modification Factor R****AA**

**Notes:**
This enimation show us the suppression is developing toward to central collisions.

## Comparison with Theory

- In central collisions, RAA <<1 at high pt, providing clear evidence for strong medium effect;
- Data favor models with large parton densities and strong coupling

- Theory curves (1-3) from N. Armesto, *et al.*, PRD 71, 054027
- (4) from M. Djordjevic, M. Gyullasy, S.Wicks, PRL 94, 112301

**Notes:**
 local transport coefficient along the path of the parton

1a: applies for the case without presence of any medium causing heavy quark energy loss. The q hat values of 4 and  14 which corresponding to 2) and 3), lead to light quark energy losses 

4) Include electrons from both D and B meson decay and correspond to initial gluon densities of dNg/dNy =1000. the present data pose a challenge to existing calculations of radiative energy loss in the medium produced at RHIC and will help to distinguish between different energy loss scenarios. 

## Open Charm Flow

- Significant anisotropy observed for non-photonic electrons
- Charm flow?
- Hadronization?
- Indication for reduction of v2 at pT > 2 GeV/c
- Bottom contribution??

- Theory:Greco, Ko, Rapp:   PLB 595 (2004) 202

**Notes:**
The transverse momentum dependence of the azimuthal anisotropy for electron at mid-rapidity has been measured in AuAu collisions. 

Upper plot shows the phenix preliminary results of non-photonic v2 vs pt with two different charm flow scenarios from this paper.
dash line corresponding to no rescattering of the initially produced charm quarks(with out flow)
solid line reflects the effect of complete thermalization (with flow)

## Summary & outlook

**PHENIX measured ****production of ****non-photonic ****e**** ****and prompt ******** in a wide**** kinematics ranges ****in p+p, d+Au and Au+Au**
**For pp collisions: **
**Non-photonic ****e**** pT spectra at y = 0 and prompt ******** p****T**** spectra at y = 1.65 are similar. **
**FONLL or PYTHIA 6.205 are under predicted Non-photonic ****e**** production at middle rapidity. The discrepancy is even larger for prompt**** ******** at forward rapidity****.****	**
**For dAu collisions:**
**Middle rapidity follows binary scaling within errors****.  **** **
**A suppression in forward rapidity**** of prompt muon production is observed. It is consistent with CGC and power correction pictures. **
**Observation of ****enhancement at backward rapidity**** needs more theoretical investigation. Anti-shadowing and recombination could lead to such enhancement. **
**For AuAu collisions:**
**Nuclear modification factor R****AA**** shows a strong suppression of the electrons at high p****T**** in Au+Au collisions. Observed R****AA**** favors models with large parton densities and strong coupling**
**Significant anisotropy observed for non-photonic electrons at y=0.**
**Ongoing analysis: AuAu prompt muon, prompt muon v****2 ****at y=2.**
**PHENIX silicon vertex detector will enable us to determine the open charm (beauty) decay vertex and give us more accurate measurement of  open heavy flavor.****  **

## Backup

## Open Charm Flow

- Significant anisotropy observed for non-photonic electrons
- Charm flow?
- Hadronization?
- Indication for reduction of v2 at pT > 2 GeV/c
- Bottom contribution??
- The shape at low pT agrees with electron v2 from D-meson decays assuming the shape of v2 (D) proportional to v2 ()

- Theory:Greco, Ko, Rapp:   PLB 595 (2004) 202

**Notes:**
The transverse momentum dependence of the azimuthal anisotropy for electron at mid-rapidity has been measured in AuAu collisions. 

Upper plot shows the phenix preliminary results of non-photonic v2 vs pt with two different charm flow scenarios from this paper.
dash line corresponding to no rescattering of the initially produced charm quarks(with out flow)
solid line reflects the effect of complete thermalization (with flow)

In order to further understand the data,

## Run02 Au+Au total cross section vs Ncoll 

**Binary scaling of total open charm yield**

- S.S. Adler, *et al.*, PRL 94 082301

**Notes:**
The total open charm cross section are binary scaled. Charm production process is point like. There is small modification in initial state parton distribution function.

## non-photonic e: 
“Cocktail subtraction” 
“Converter subtraction”

 Prompt μ: 
Punch-through hadrons: 
Data driven method to Estimate  attenuation
Decay muons: Vertex dependent analysis

- “Cocktail subtraction”
- “Converter subtraction”
-  **Prompt ****μ: **
- Punch-through hadrons:
- Data driven method to Estimate  attenuation
- Decay muons: Vertex dependent analysis

**Analysis Techniques: (semi-lepton channel)**

- Muon
- detector

**Notes:**
calculation of “photonic” electron background from all known sources 
extraction of “photonic” electron background by special run with additional converter
Both analyses clearly show an excess “non-photonic” electron signal attributed to heavy flavor decays 

## Sources of prompt muons (pT> 0.9GeV) (determined from Pythia)

**Sources of prompt muons (p****T****> 0.9GeV) (determined from Pythia)**

- D±±, ... , c++,

- B±  ±

- ±  ±

- *  + -

- q q  *  + -

- J/,...  + -

- , ,  + -

- charge asymmetric

- charge symmetric

## Analysis Techniques: prompt muon 

- 	**N****inclusive****=**** ****N****prompt**** + ****(N****punch-through**** + N****decay-muon****)**
- Punch-through hadrons:
- Data driven method:
-    Estimate  attenuation
- Decay muons
- Vertex dependent

**Analysis Techniques: **prompt muon

## Analysis Techniques: Muons from hadron decay

**Analysis Techniques: **Muons from hadron decay

- North arm

**Notes:**
Let’s take a closer look at muon detector near the collision point. The pi, k which produced far from muon arms will have high probobility to decay. 

muon from the light hadron decay have been measured. After we subtract the punch through  and decay muon contribution, we got prompt muon signal, 

Rdau define at fix z vertex. 
Muon yield increases as a function of distance from the  absorber - due to muons from p/K decays 
Linear shape of z vertex slope, because ct g ~100 [m]. 

## PHENIX published Run02 results

- Binary scaling of total open charm yield

- S.S. Adler, *et al.*, PRL 94 082301