# Presentation: 754088

## New Prospects for locating the QCD Critical End Point (CEP) at RHIC

## A Central Question for the QCD Lab!  

***A Central Question for the QCD Lab!  ***

**The location of the critical End point and the phase boundaries are fundamental to the QCD phase diagram***** !***

## Theoretical Guidance ?

***Theoretical Guidance ?***

*Any search for the CEP** **requires investigations*
*over a broad range of **μ** & T.*

## For the first time (at last) we 

- For the first time (at last) we
- have access to the full range
- Of μ and T.
- (via Energy scans at
- RHIC, SPS & FAIR)

## Better News !

- This is a necessary
- requirement for locating
- the CEP

*The Crossover Transition to the QGP is made clear at RHIC*
*Space-time measurements*
*Flow Measurements*
*Jet Quenching *

***Better News !***

* **2) The viscosity to entropy ratio offers a new dynamical probe for the CEP*
* **Contrasts  Stationary State   variables*

## Life Time measurements

**QGP and**
**hydrodynamic expansion**

**hadronization**

_**The Role of Femtoscopy**_

**Are source Imaging measurements consistent with the crossover transition ?**

**A Cross Over strongly affects **
**the Space-time Dynamics**

**Theory indicate a crossover transition**

**The space-time extent (Source Image) can lend crucial insights**

- Puzzle ?

**Life Time measurements**
**As a probe for the transition**

## Why source Imaging?

**Source Imaging gives access to important space-time information **
**which is inaccessible via “traditional approach”**

## Source Imaging Methodology (1D)

**Source Imaging Methodology (1D)**

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

_**1D Koonin Pratt Eqn.**_

***Reliable measurement of the full***
***1D Source Function ! ***

## Source Imaging Methodology (3D)

**Source Imaging Methodology (3D)**

_**3D Koonin Pratt Eqn.**_

***Reliable measurement of the full Source Function in 3D ! ***

## PHENIX Data

***Robust Experimental Source Functions obtained from moments***

**PHENIX Data**

- Contributions from
- l > 6 is negligible

## The transition is Not  a Strong 

***Source Function Comparison to Models Give robust life time estimates ************ Consistent with Crossover transition***

- _Therminator:_
- A.Kisiel et al. Comput.Phys.Commun.174, 669 (2006)
**Thermal model with Bjorken longitudinal  expansion and transverse Flow**
-  Spectra & yields constrain thermal properties
-  Transverse radius ρmax : controls
-    transverse extent
-  Breakup time in fluid element rest frame,
-       : controls longitudinal extent
-  Emission duration     : controls tails in
-   long and out directions
-   a controls x-t  correlations

**The transition is Not  a Strong **
**First order Phase Transition?**

## QM-2008

*Poster 189*
*Mikolaj Chojnacki, Wojciech Florkowski, Wojciech Broniowski, Adam Kisiel*
*arXiv:0712.0947[nucl-th]*

## The Flow Probe

***Substantial elliptic flow signals should be present for a variety of particle species   ************  ************  Constraints for sound speed and viscosity***

***From E******T****** Distributions***

***Expect Large Pressure Gradients ************ Hydro Flow***

**The Flow Probe**

***Control Params.***

## We hold these truths to be self evident !

**initial state**

**pre-equilibrium**

**QGP and**
**hydrodynamic **
**expansion**

**hadronization**

**hadronic phase**
**and freeze-out**

_**Courtesy S. Bass**_

**We hold these truths to be self evident !**

*Scaling for identified hadrons** *

*Scaling for Heavy Quark** *

*Scaling for Phi Mesons** *

*Universal Scaling** *

## The expected saturation of v2

**Saturation of Elliptic flow consistent with a  soft EOS associated with Crossover**

**The expected saturation of v****2**
**Is observed **

**Phys.Rev.Lett.94:232302,2005*** *

## Partonic Fluid Flow 

_**Model **_
_**Comparison**_

**Partonic Fluid Flow **
**Is near Perfect**

***1-2 X the conjectured lower bound***

## A Crossover transition to the strongly coupled thermalized QGP occurs at RHIC

**initial state**

**pre-equilibrium**

**QGP and**
**hydrodynamic expansion**

**hadronization**

**hadronic phase**
**and freeze-out**

_**Courtesy S. Bass**_

**A Crossover transition to the strongly coupled thermalized QGP occurs at RHIC**

**We hold these truths to be self evident !**

## Transport Coefficient

**Transport Coefficient**

***Thermalization facilitated by 2************3 processes***

*C. Greiner et al*

## Small viscosity results in

**Small viscosity results in**
**large suppression**

*An estimate of the scattering power*

## Setting an upper limit on 

**QCD Sonic Boom**

***Gives sound speed directly;  Sets upper limit on viscosity.***

**Setting an upper limit on **
**The viscosity**

## (2+1) processes efficiently removed via two-event mixing to obtain true three particle correlations

**(2+1) processes efficiently removed via two-event mixing to obtain true three particle correlations**

**Validation test of the use of two event mixing to remove  2+1 processes**

## QCD Sonic Boom?

**The data validates the presence of a  Mach Cone away-side jet **

**Total 3PC jet correlations**

**QCD Sonic Boom?**

## Hints of the CEP?

**Hints of the CEP?**

## How to get there?

**How to get there?**

**Lacey et al.**
**arXiv:0708.3512** [nucl-ex]* *

## How to find the CEP?

**How to find the CEP?**

***First estimate   T ~ 165-170  ******μ****** ~ 120-150 MeV***
***Need two energies ******immediately***