# Presentation: 537914

## Evidence for a long-range pion emission source in Au+Au 

**Nuclear Chemistry, **
**SUNY, Stony Brook**

***Evidence for a long-range pion emission source ******in Au+Au ***
***Collisions at ***

## Outline

** ****Motivation**
** ****Brief Review of Correlation analysis methods**
**Data Analysis & Results**
**Correlation functions**
**Source functions**
**Source parameters & dependence (centrality, mT, etc)**
**Conclusion/s**
**                **

## Conjecture of collisions at RHIC :

**Conjecture of collisions at RHIC** :

- Motivation

**Which observables & phenomena connect **
**to the de-confined stage?**

**Courtesy S. Bass**

## One Scenario:

**hydrodynamic expansion**

_**One Scenario**__:_

- Motivation

_**Expectation:**_
**A de-confined phase leads to an emitting system characterized by a much larger space-time extent than** **would be expected from a system which remained in the hadronic phase **

- Increased System Entropy that survives hadronization

## Experimental Setup

**PHENIX Detector**
**Several Subsystems exploited for the analysis**

**Excellent Pid is achieved**

## Cuts

- Dphi (rad)

- Dz (cm)

## Cuts

- Dz (cm)

- Dphi (rad)

## Analysis Summary

**Image analysis in PHENIX Follows three basic steps.**
** **
** ****Track selection**
** ****Evaluation of the**
**    ****Correlation Functions (with pair-cuts etc.)**
** ****Imaging of **
**    ****Correlation functions**
**    ****Fits to correlation function**

- Dphi >0.02 dz < 5 cm
- Dphi >0.01 dz > 5 cm

## Correlation Function

**Correlation Function**

**Direct Fits to the**
**Correlation Functions**

**Imaging **

**Source **
**Function**

## Imaging Technique

**Technique Devised by:**
** **
**D. Brown, P. Danielewicz,**
**PLB 398:252 (1997).** **PRC 57:2474 (1998).**

**Inversion of Linear integral equation to obtain source function**

**Source function**
**(Distribution of pair separations)**

- Encodes FSI

**Correlation**
**function**

**Inversion of this integral equation**
**==******** ****Source Function**

- 1D Koonin Pratt

## Imaging 

_**Inversion procedure**_

## Results

**  *****Non Gaussian tail observed in source function***

## Results

***Results***

## Results

***Results***

## Correlation Fits

**Parameters of the source function**

- Minimize Chi-squared

- [Parameterized form for S(r)]
- + convolution with kernel
-  calculated C(q)

- Measured correlation function

## Extraction of Source Parameters

_**Fit Function **__**(Pratt et al.)**_

**This fit function allows extraction of both **
**the short- and long-range **
**components of the source image**

- Bessel Functions

- Radii

- Pair Fractions

## Input source function recovered

**Input source function recovered**
**Procedure is Robust !**

***Quick Test - 1***

## Fitting correlation functions

_**Kinematics**_
**“****Spheroid/Blimp” Ansatz**

**Brown & Danielewicz PRC 64, 014902 (2001)**

- “spheroid/Blimp” parameters

## Fix RT = R and vary a 

**Fix R****T ****= R and vary a **
**Source parameters **
**Recovered**

***Sensitivity Tests***

## Fix a and vary R 

**Fix a and vary R **
** **
**Source parameters Recovered**

***Sensitivity Tests***

## Results

***Results***

## Comparison of  Source Functions

**Same source functions from different parameterization**

***Comparison of  Source Functions***

## Short and long-range components of the source

- Short-range 

- Long-range 

- T. Csorgo
- M. Csanad

## Short and long-range components of the source

***Short and long-range components of the source***

- T. Csorgo
- M. Csanad

## Short and long-range components of the source

- T. Csorgo
- M. Csanad

- Core Halo assumption

- Expt 

## Next Steps; 3D imaging/moment fitting

***Next Steps; 3D imaging/moment fitting***

**Higher l moments ******** angular deformation of source**

## Next Steps; 3D imaging/moment fitting

- Solid proof of principle

- Simulation
- results

## Summary

** ****First Extensive study of two-pion 1D source **
**images in Au+Au collisions at RHIC**
** ****Results indicate evidence for non-Gaussian tail**
** ****Long-range behavior of source function ~ 3x short-range**
** ****Centrality dependence of radius parameters and lambda   **
**Fraction in compatible with simple estimate of omega decay**

**Further detailed 3D analysis in progress to**
**pin-down origin of long-range behavior**

***Summary***