# Presentation: 108214

## Excitation FunctionExperimental Perspective-- search for the native hadronic shoreNu XuLawrence Berkeley National LaboratoryMany thanks to organizers andV. Koch, J. Randrup, H. Ritter, Z. Xu

## Outline

**Motivation **
**What we have learned at 200GeV**
**	****Some systematic from 1 - 200 GeV**
**Energy scan at RHIC - search for native hadronic shore**

## High-Energy Nuclear Collisions

_**Goals:**_
**(1) Identify the bulk-matter (EOS) with partonic d.o.f**
**(2) Study the properties of the partonic matter**
**(3) *****Demonstrate***** the transition between partonic and hadronic worlds**

## Yields ratio results

-  In central collisions, thermal model fit well with S = 1. **The system is thermalized at RHIC.**
-  Short-lived resonances show deviations. **There is life after chemical freeze-out.**
-                                          RHIC white papers -  2005, Nucl. Phys. _*A757*_, STAR: p102; PHENIX: p184.

## Collectivity, Deconfinement at RHIC

-  -  v2, spectra of light hadrons
-     and multi-strange hadrons
-  -  scaling of the number of
-     constituent quarks
-  At RHIC, I believe we have
-  achieved:
****** ****Partonic Collectivity**** **
****** ****Deconfinement***** ***
*PHENIX**: PRL*_***91***_*, 182301(03)      *
*STAR**: PRL*_***92***_*, 052302(04), *_***95***_*, 122301(05)*
*           **nucl-ex/0405022*
*S. Voloshin, NPA715, 379(03)*
*Models: Greco et al, PR*_***C68***_*, 034904(03)*
*X. Dong, et al., Phys. Lett. *_***B597***_*, 328(04).*
*...**.*

## -meson flows

- STAR Preliminary, QM05 conference

- RHIC results mean:
- Partonic EoS
- Particle productions dominated via partonic introduction
- The system started beyond hadronic matter
-   Is there a boundary that can be observed?
-   Where is the boundary?
-   **Experimental issue!**
-   Systematic approach

## Non-photonic electron spectra & v2

- Partonic energy loss - necessary for the plasma formation !
***Charm flows -  a hint for partonic thermalization at RHIC!***

## Freeze-out systematic

- At freeze-out:
- The ‘temperature’ parameters Tfo seem to be around 100 -140 MeV.
- v2 continuously rise with beam energy. A clear increase in averaged velocity parameters r - increase of the ‘pressure’ in the system at RHIC.
- When v2 crosses zero, a plateau appears for Tfo and r at beam energy ~ 5 GeV.

## Nuclear Phase Diagram

- High excitation
- Partonic d.o.f. dominant
***“******Tsunami at deep ocean”***
***Null effect!!!***

- Energy scan:
**Turn off partonic activities**
-   - ,, D-meson v2  0
-   - jet-quching disappear
- Look for our
***“******Native hadronic shore”***
- Systematic study of correlation/fluctuations
- Systematic of di-lepton signal
- U+U collisions
- Large acceptance with collider environment

## Detector system

- Clean environment - colliding mode
- Large acceptance
- Good resolutions for particle PID
- STAR TPC
- STAR TOF(08)        ideal for the scan program
- STAR HFT(10)
- PHENIX HBD 	ideal for di-lepton program

**Important for RHIC-II future programs**
**  **_**Heavy flavor program**_**: **
**	****partonic EoS study**
**  **_**Energy scan**_**: **
**	****phase boundary and possible critical point**