# Presentation: 009432

## Non-Photonic Electron-Hadron Correlations at STAR

- Non-Photonic Electron-Hadron Correlations at STAR

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

- Gang Wang, Quark Matter 2008

## Outline

-  Motivation
-  Analysis procedure
-  e-h correlations in p+p collisions
-  e-h correlations in Cu+Cu collisions
-  e-h correlations in Au+Au collisions
-  Summary

- Gang Wang, Quark Matter 2008

## 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**

- Gang Wang, Quark Matter 2008

## Non-photonic electrons

**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, Quark Matter 2008

## 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, Quark Matter 2008

## 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), 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, Quark Matter 2008

## Electron ID Using TPC, BEMC and BSMD

**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: ****above 99% for ****3 < *****p******T***** < 6 GeV/*****c***** in CuCu and AuAu;****above 98% for        3 < *****p******T***** < 6 GeV/*****c*****, and 80% for 9 GeV/*****c***** in p+p collisions.**

- Gang Wang, Quark Matter 2008

## 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****.**

- Gang Wang, Quark Matter 2008

## 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-w/-partner**** **
**	****      – ****(1/eff -1)*(****Δφ****OppSign-w/o-partner**** – ****Δφ****SameSign-w/o-partner****)**

- Each item has its own corresponding Δφ histogram.

- Gang Wang, Quark Matter 2008

## Near Side in p+p

**Near Side in p+p**

- Gang Wang, Quark Matter 2008

## 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**

- Gang Wang, Quark Matter 2008

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

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

- See *Shingo* *Sakai*’s poster

**Substantial bottom contributions**

- Gang Wang, Quark Matter 2008

## Away Side in CuCu and AuAu

**Away Side in CuCu and AuAu**

- Gang Wang, Quark Matter 2008

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

**Uncertainty from ZYAM**

**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***

- STAR Preliminary

**On the away side, a broad structure or a possible double-hump feature has been observed, even before v****2**** subtraction.**

**Non-photonic e-h azimuthal correlation is measured in one ****π**** range,**
**and open markers are reflections. We see clear correlation structures.**

- Gang Wang, Quark Matter 2008

## 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 (****66.5%, 60%, 70%****).**

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

- STAR Preliminary

- Gang Wang, Quark Matter 2008

## 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, Quark Matter 2008

## Interpretation

**Interpretation**

**In PYTHIA, B + D contribution has only one peak on the away side, unlike the experimental result in CuCu. ****PYTHIA fit**** has a big chi2.**

**The away side in e-h is similar to what has been observed in h-h correlations, and consistent with Mach Cone calculations *****etc*****.**

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

- Gang Wang, Quark Matter 2008

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

**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.**

**0 – 20%: 3 < *****p******T******trig***** ****< 6 GeV/*****c***** & 0.15 < *****p******T******asso***** ****< 1 GeV/*****c***

- STAR Preliminary

- Gang Wang, Quark Matter 2008

## Summary

-  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.
-  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!

- Gang Wang, Quark Matter 2008

## Back up slides

- Gang Wang, Quark Matter 2008

## 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, Quark Matter 2008

## Electron Identification: P/E

-  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.

- Gang Wang, Quark Matter 2008

## 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, Quark Matter 2008

## 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, Quark Matter 2008

## 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, Quark Matter 2008

## PYTHIA simulations with AuAu yields

**PYTHIA simulations with AuAu yields**

**In PYTHIA,**** ****non-photonic e-h correlation functions show different B and D contributions on the near side, and similar on the away side.**

**3 < *****p******T******trig***** ****< 6 GeV/*****c***** & 0.15 < *****p******T******asso***** ****< 1 GeV/*****c***

- Gang Wang, Quark Matter 2008

## Middle steps in CuCu 200 GeV

**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***** ****< 1 GeV/*****c***

- Gang Wang, Quark Matter 2008