# Presentation: 923611

## Non-Photonic Electron-Hadron Correlations at RHIC/STAR

- Non-Photonic Electron-Hadron Correlations at RHIC/STAR

**Gang Wang**
**(*****University of California, Los Angeles*****)**
***for ******STAR****** Collaboration***

- Gang Wang, UCLA Workshop 2009

## Outline

-  Motivation
-  Analysis procedure
-  Near-side contribution in p+p collisions
-  Away-side broadness in A+A collisions
-  Summary

- Gang Wang, UCLA Workshop 2009

## Motivations 

**Conical Pattern in ****2-Particle Correlations in Au+Au Collisions**

***p******T******trig*****    ****= 2.5-4.0 GeV/*****c*****; **
***p******T******asso***** = 1.0-2.5 GeV/*****c***

- Motivations

***Mark Horner (for STAR Collaboration)****:** *
*J. Phys. G: Nucl. Part. Phys. ****34**** (2007) S995*

**Further support by 3-particle correlations**

- See STAR paper on 3-particle correlations at *arXiv:0805.0622v2 (accepted by PRL)*

**Conical Pattern**

- Gang Wang, UCLA Workshop 2009

## Motivations 

**How does B/D lose energy? Via conical emission?**

**Conical Pattern in ****2-Particle Correlations in Au+Au Collisions**

***p******T******trig*****    ****= 2.5-4.0 GeV/*****c*****; **
***p******T******asso***** = 1.0-2.5 GeV/*****c***

- Motivations

***Mark Horner (for STAR Collaboration)****:** *
*J. Phys. G: Nucl. Part. Phys. ****34**** (2007) S995*

**Near Side:**
**what’s the contribution of B/D decay to the non-photonic electrons?**

**trigger**

**What if we trigger on non-photonic electrons?**

- Gang Wang, UCLA Workshop 2009

## Study of heavy flavor via non-photonic electrons

**Study of heavy flavor via non-photonic electrons**

** ****D ****mesons have their directions well represented by the daughter electrons,**** above 1.5 GeV/*****c*****.**
** ****Electrons from ****B**** decays can represent the B meson momentum direction well**** if *****p******T***** > 3 GeV/*****c*****.**

**PYTHIA**

- Gang Wang, UCLA Workshop 2009

## B vs D: contribution to non-photonic e

**B vs D: contribution to non-photonic e**

**PYTHIA**** shows significant differences in B&D on the ****near-side**** correlations in ****p+p**** collisions, and we can fit the experimental data to obtain B/D contribution.**

**p****T_asso**** > 0.3 GeV/c**

- Gang Wang, UCLA Workshop 2009

## Major Detectors Used

** ****Time Projection Chamber (TPC)**
** ****Barrel Electro-Magnetic Calorimeter (BEMC)**
** ****Barrel Shower Maximum Detector (BSMD)**

**Data Sample:**
**At ********s****NN ****= 200 GeV,**** **
**p+p collisions ****in run6 (2006),    d+Au collisions in run8 (2008)****,**** ****Cu+Cu collisions in run5 (2005), Au+Au collisions in run7 (2007).**

**Signal: **
**Non-photonic electron**
**Background: **
**Hadron Photonic electron**

**Charm decay**
**Bottom decay**

**Photon conversion**
**π****0** **Dalitz decay**
**η** **Dalitz decay**
**kaon decay**
**vector meson decays**

**Major Detectors Used**

- Gang Wang, UCLA Workshop 2009

## Electron ID Using TPC, BEMC and BSMD

**With BEMC and BSMD, the electron peak is enhanced in the energy loss distribution, and we obtain a very pure electron sample.****   **

**Purity****dAu, CuCu, AuAu: ****above 98% for ****3 < *****p******T***** < 6 GeV/*****c*****p+p collisions: above 98% for        3 < *****p******T***** < 6 GeV/*****c*****; 80% for 9 GeV/*****c*****.**

**calibrated Log(dE/dx)**

- Gang Wang, UCLA Workshop 2009

## Photonic Background

**Photonic Background**

-  **The invariant masses of the OS and SS e-pairs have different distributions.**
-  **Reconstructed photonic electron is the subtraction.**
-  **Photonic electron is the** **reconstructed-photonic/ ****ε**
** ****ε**** is the background reconstruction efficiency calculated from simulations****.**

**Azimuthal angles are not used in the invariant mass calculation. Angle and dca cuts were applied between e pairs.**

- Gang Wang, UCLA Workshop 2009

## Procedure to Extract the Signal of e-h Correlations 

**Procedure to Extract the Signal of e-h Correlations**

**Semi-inclusive electron**

**Δφ****non-pho**** =  ****Δφ****semi-incl**** +  ****Δφ****SameSign ****– (1/eff -1)*(****Δφ****OppSign**** – ****Δφ****SameSign****)**

- Each item has its own corresponding Δφ histogram.

- Gang Wang, UCLA Workshop 2009

## Near-Side contribution in p+p

**Near-Side contribution in p+p**

- Gang Wang, UCLA Workshop 2009

## Non-photonic e-h correlations in p+p 200GeV

-  Clear azim. correlation is observed around near and away side.
-  Fitting measured dn/dφ distribution from B and D decays, we can estimate B   decay contribution to non-photonic electron.

**Non-photonic e-h correlations in p+p 200GeV**

- B

- D

- Gang Wang, UCLA Workshop 2009

## B contribution to non-photonic e in p+p 200GeV

**B contribution to non-photonic e in p+p 200GeV**

- Gang Wang, UCLA Workshop 2009

## Large bottom energy loss?

- RAA for non-photonic electron is consistent with hadron’s.
- This Indicate large energy loss
- not only charm quark
- but also bottom quark.

**Large bottom energy loss?**

- With the measurements of r @ pp and RAA, we can derive a relationship between RAAec and RAAeb.

- non-*γ** e*

- hadron

- Gang Wang, UCLA Workshop 2009

## RAAec & RAAeb correlation

-  RAAec & RAAeb correlation
-   together with models
-  Dominant uncertainty is
-    normalization in RAA analysis
-  RAAeb < 1; B meson is also suppressed
-  prefer Dissociate and
-              resonance model
-              (large b energy loss)

*I: Phys. Lett. B 632, 81 (2006); *_*dN*__*g*__*/dy = 1000*_
*II: Phys. Lett. B 694, 139 (2007)*
*III: Phys.Rev.Lett.100(2008)192301*

- STAR preliminary

- pT > 5 GeV/c

- RAAec & RAAeb correlation

- Gang Wang, UCLA Workshop 2009

## Away-side broadness in A+A

***d+Au collisions serve as a reference of the cold nuclear matter...***

- Gang Wang, UCLA Workshop 2009

## Non-photonic e-h correlations in d+Au 200 GeV

**Non-photonic e-h correlations in d+Au 200 GeV**

**Non-photonic e-h azimuthal correlation is measured in one ****π**** range,**
**and open markers are reflections.****  ****The away-side correlation can be well described by ****PYTHIA****. No medium effects**** ****seen here.**

**3 < *****p******T******trig***** ****< 6 GeV/*****c***** & 0.15 < *****p******T******asso***** ****< 0.5 GeV/*****c***

- STAR Preliminary

- Gang Wang, UCLA Workshop 2009

**Notes:**
Eff = 70%

## Non-photonic e-h correlations in Cu+Cu 200 GeV

**Non-photonic e-h correlations in Cu+Cu 200 GeV**

**Upper limits of v****2**** used are 60% of *****hadron***** v****2**** values measured with the v****2****{EP} method (equivalent to v****2****{2}). **

**0 – 20%: 3 < *****p******T******trig***** ****< 6 GeV/*****c***** & 0.15 < *****p******T******asso***** ****< 0.5 GeV/*****c***

**On the away side, there’s a broad structure or a possible double-hump feature, even before v****2**** subtraction. ****PYTHIA fit**** has a big *****χ******2*****.**** **

- Gang Wang, UCLA Workshop 2009

**Notes:**
Eff = 65.7%

## Possible interpretations

**Possible interpretations**

**The away side in e-h is similar to what has been observed in h-h correlations, and consistent with Mach Cone calculations *****etc*****. The charm jet deflection provides an alternative interpretation.**

**3 < *****p******T******trig***** < 6 GeV/*****c***** & 0.15 < *****p******T******asso***** < 0.5 GeV/*****c***

- Gang Wang, UCLA Workshop 2009

## Non-photonic e-h correlations in Au+Au 200 GeV

**Non-photonic e-h correlations in Au+Au 200 GeV**

**Upper limits of v****2**** used are 80% of *****hadron***** *****v******2***** values measured with the v****2****{EP} method. Non-photonic e-h correlation is broadened on the away side. ****PYTHIA fit**** has a big *****χ******2*****.**** **

**0 – 20%: 3 < *****p******T******trig***** ****< 6 GeV/*****c***** & 0.15 < *****p******T******asso***** ****< 0.5 GeV/*****c***

- STAR Preliminary

- Gang Wang, UCLA Workshop 2009

**Notes:**
Eff = 62.5%

## Summary I

-  We have measured non-photonic e-h correlations in p+p collisions to retrieve B and D contributions to non-photonic electrons up to *p**T*~9 GeV/*c*.
-  We found comparable B and D contributions for electron *p**T* 5.5~9 GeV/*c*.
-  FONLL prediction and our eB/(eB+eD) results are consistent with each other within errors.
-  Our measured B/D ratio would imply considerable b quark energy loss in medium based on RAA measurement from central Au+Au collisions. One more measurement is needed: RAAeb, RAAec or r@A+A.

- Gang Wang, UCLA Workshop 2009

## Summary II

-  Using the d+Au collision as a reference, the shape of non-photonic e-h azimuthal correlation function is found to be modified in central Cu+Cu and Au+Au collisions due to the presence of the dense medium created in these collisions.
-  Away-side**: **Hint of a broad structure, similar shape to that from h-h correlations.
-  Induced by heavy quark interaction with the dense medium?
-  Quantitative measure and investigation of the nature of the possible conical emission pattern will require more statistics! DAQ1000 will help us there! *Will try 3-particle correlations!*
*We have demonstrated the feasibility of the analysis on *
*the jet-medium interaction tagged by a heavy quark.*

**Summary II**

- Gang Wang, UCLA Workshop 2009

## Back up slides

- Gang Wang, UCLA Workshop 2009

## HQ Production Mechanism

**HQ Production Mechanism**

**Due to large mass, HQ productions are considered as point-like pQCD processes**
**HQ is produced at the initial via leading gluon fusion, and sensitive to the gluon PDF**** **
**NLO pQCD diagrams show that Q-Qbar could be not back-to-back in transverse plane **
**We need to study this smearing effect with models**

****** ******** ******

****** ******** ****0**

****** ******** ******

- flavor creation

- gluon splitting

- Gang Wang, UCLA Workshop 2009

## Yields in d+Au 200 GeV

**Yields in d+Au 200 GeV**

**Trigger name**:
- High Tower (|Vertex Z| < 40 cm)
**Production**:
- P08id, production_dAu2008** **
- 0.7M events with matched tracks
**High-tower trigger electrons**
**(3 < Pt < 6GeV/c, |eta| < 0.7)** :
**Inclusive**: ~ 7399
**Photonic: ~ **2826

- Charged hadrons

- electrons

- Gang Wang, UCLA Workshop 2009

## Electron Identification: P/E

**Electron Identification: P/E**

**3 < *****p******T******trig***** < 6 GeV/c**

-  P is measured by TPC. E is the sum of the associated BEMC point’s energy measured by BEMC.
-  Electrons will deposit almost all of their energy in the BEMC towers. 0.3 < P/E <1.5 was used to keep electrons and reject hadrons.

- Charged hadrons

- electrons

- Gang Wang, UCLA Workshop 2009

## Electron Identification: Shower Size

-  Number of SMD hits per shower indicates shower size.
-  Electrons have larger number of BSMD hits than those for hadrons.
-  Electron candidates have to satisfy Number of BSMD hits > 1.

- Gang Wang, UCLA Workshop 2009

## Electron Identification: Projection Distance

-  -3σ < Z-Dist < 3σ and -3σ < Phi-Dist < 3σ were set to remove lots of random associations between TPC tracks and BEMC points.

- Gang Wang, UCLA Workshop 2009

## PYTHIA simulations

**PYTHIA simulations**

**B**

**D**

**For each p****t**** bin, the non-photonic e-h correlations B_corr and D_corr are combined according to B’s and D’s relative contributions to the non-photonic electrons:**
**(e****B*****B_corr + e****D*****D_corr) / (e****B****+e****D****)**

**Each pt bin is weighted with their relative yields, and then they are summed up.**

- Gang Wang, UCLA Workshop 2009

## PYTHIA simulations weighted with CuCu yields

**3 < *****p******T******trig***** < 6 GeV/*****c***** & 0.15 < *****p******T******asso***** < 0.5 GeV/*****c***

**Here we assume the B/D contribution in CuCu is similar to that in p+p. Even if they are not similar, we don’t expect the double-hump without a medium.**

**B**

**D**

- Gang Wang, UCLA Workshop 2009

## Middle steps in CuCu 200 GeV

**Semi+Comb and Photonic show different correlations.**

**0 – 20%: 3 < *****p******T******trig***** ****< 6 GeV/*****c***** & 0.15 < *****p******T******asso***** ****< 0.5 GeV/*****c***

- Gang Wang, UCLA Workshop 2009

## Robustness in CuCu 200 GeV

**Robustness in CuCu 200 GeV**

**The broad structure on the away side is robust when we vary the efficiency of photonic electron reconstruction (****65.7%, 60%, 70%****).**

**0 – 20%: 3 < *****p******T******trig***** ****< 6 GeV/*****c***** & 0.15 < *****p******T******asso***** ****< 0.5 GeV/*****c***

- Gang Wang, UCLA Workshop 2009