# Presentation: 620670

## Identified “High” pT particle Correlations

- Ying Guo
*Wayne State University*
*For STAR Collaboration*

***Hot Quark 2004***

## Outline

- Introduction
- Data analysis
- Preliminary results
- Discussion

## Motivation:

- Get a better understanding of the high pT azimuthal correlations
- Particle identified jet correlation study provides us additional information about  the jet quenching and particle production mechanisms.
- The strange particle identified jet correlation can be used as a probe to study the flavor dependence of the strong interaction and the fragmentation process.

## Medium Quench effect of the High pT particles

- Medium Quench effect of the High pT particles

- Potential improvement of the original measurements
- background subtraction method
- variable away side range *(**Δφ**)*

**Phys. Rev. Lett. 90 (2003) 082302**

**nucl-ex/0407007**

**Phys. Rev. Lett. 91 (2003) 172302**

## Jet profile Reconstruction down to low pT:  4.0 Gev/c<pT,trigger <6.0 Gev/c, 0.15 Gev/c<pT,associate <5.0 Gev/c

- Fuqiang’s QM2004 talk.

## Sample of correlation Function:

-  Jet Fragmentation (near side) multiplicity
-  Jet quenching (away side)
-  Momentum conservation (away side)
-  Other particle production mechanism
-      Coalescence, recombination

## Data Analysis Methods:

- pp:

-  Au + Au:

*Gaussian Fit of back side:*

*Cosine Fit of back side (momentum balance):*

*Same Side*

*Back Side*

*Background*

- Parameters are compared for different fits for two different pT cuts as the function of centralities

## Λ +h (charged hadrons) correlations AuAu and pp

- Λ +h (charged hadrons) correlations AuAu and pp

- 0-5%

- 10-30%

- 5-10%

- 30-50%

- 50-70%

## Λ +h correlations AuAu (cosine fit)

## Width (Λ+h)

**1.5<p****T,trigger****<3.0, 1.5<p****T,asso****<3.0**

**2.5<p****T,trigger****<4.0, 1.7<p****T,asso****<2.5**

- Width (Λ+h)

- Gaussian fit

- Cosine fit

## Associated particle yields (Λ+h)

**1.5<p****T,trigger****<3.0, 1.5<p****T,asso****<3.0**

**2.5<p****T,trigger****<4.0, 1.7<p****T,asso****<2.5**

- Gaussian fit

- Cosine fit

## AA/pp (Λ+h)

**1.5<p****T,trigger****<3.0, 1.5<p****T,asso****<3.0**

**2.5<p****T,trigger****<4.0, 1.7<p****T,asso****<2.5**

- Gaussian fit

- Cosine fit

- No pp reference

- Large AA/pp ratio for the same side
- Trigger Bias?
***X N Wang, nucl-th/0405017***

## same and away side yields of different particle species

## Same side width of different particle species

- Lambda

- Anti Lambda

- K0 short

## PHENIX measurementfrom QM2004

- SAME SIDE

## PHENIX measurementfrom QM2004

- PHENIX measurementfrom QM2004

## 1.5 GeV/c < pT,trig,pT,asso<3.0 GeV/c

## Summary:

- We can measure identified particle correlations
- For central collisions, large width(>π/2~1.6) of the back side indicates a momentum balance shape and collapse of the Jet structure.☺
- Same side AA/pp ratio appears to be large in the intermediate pT range

**Trigger particle species dependence:**
- comparable to PHENIX measurements
- No significant particle species dependency
- No strong centrality dependency, need further study on the systematic

**Measurement of ****N**** could provide us information about how the jet get quenched inside the medium, what is the scare of particles interacted with the quenched jet.**

## Backup

## Hh AA/pp ratio for G fit

## Momentum Balance measurement comparing to balancing over the large amount of particles   by assuming  α  ~ 1.0

**Momentum Balance measurement comparing to balancing over the large amount of particles   **by assuming  α  ~ 1.0

## Fig. 11   Charged Hadrons correlations for different trigger PT range

**Back side correlations between charged hadrons:**

**Fig. 11   Charged Hadrons correlations for different trigger P****T**** ****range**

**Fig. 12  Same side and back side as function of Trigger P****T**** **

*same side is calculated by integrating the Gaussian component and the back side is calculated by integrated the cosine component. Notices that there is a clear back side signal for higher ****p******T,trigger****** ****values*

**Trigger P****T**

***Fitting Function:***

**Trigger P****T**

*In Fig.13 the C**cos** fit values  are compared to an estimate of the momentum conservation effect [6].*

**Fig. 13**

## Hence α can be measured by studying the statistical pT fluctuations of the back side jet cone compared to inclusive background

## Uncorrelated backgrounds

- Seems works pretty well!!

## L+h cos fit 1

## L+h vs. Anti-L+h (most central)

## L+h cut 2

## al+h cos fit 

## K0 short +h fit

##  h+h AA

## Hh fit