# Presentation: 122344

## High pT identified charged hadron v2 and v4 in 200GeV AuAu collisions by the PHENIX experiment  

***Shengli Huang***
***Vanderbilt University***
***   ******for the PHENIX Collaboration***

## Observables and Motivation

***S.L. Huang QM08***

*Observables **and **Motivation*
*Analysis methods*
*Results and Discussion*
*Conclusions*

***Outline:***

## Anisotropic flow v2 and v4

***S.L. Huang QM08***

- Peter Kolb, PRC 68, 031902

**  ****Azimuthal correlation with the reaction plane **
**  ****Built up in the early stage and self-quenched, therefore supply the early information of matter generated in the collision **

##     Partonic Flow

***SL Huang QM08***

***    ******Partonic Flow***

***PHENIX,***_***[ ](http://link.aps.org/abstract/PRL/v99/e052301)***__[PRL. 99, 052301 (2007) ](http://link.aps.org/abstract/PRL/v99/e052301)_

- Baryon and meson elliptic flow follow the number of constituent quark scaling as a function of KET. This indicates that partonic flow builds up at RHIC
- Where is the break point where the hydro interfaces with jet fragmentation?
- The medium density and strength of interactions The dynamic range of the
- global partonic flow
- How about the higher order anisotropic flow such as v4?

- baryon

- meson

## V4/(v2)2 ratio 

***S.L. Huang QM08***

***V******4******/(v******2******)******2****** ratio ***

**v****4**** /v****2****2**** is a probe of ideal **
**hydro behavior and related to **
**the degree of thermalization!**
***Peter Kolb, PRC 68, 031902***
***R.S.Bhalerao et.al PLB 627,49; ***
***Borghini and Ollitrault, PLB642,227 ***
**Hydro dynamics predicts **
**v****4**** /v****2****2 ****~0.5   **
**The identified particles **
**v****4****/v****2****2****  ratio should provide more **
**detailed information than **
**that of charged hadron**

##     How to Coalesce?

***SL Huang QM08***

***    ******How to Coalesce?***

- a) Similar momentum space

- b) Different momentum space

**The measurement of meson and baron v****4**** /v****2****2**** ratio **
**   ****will allow us to extract the partonic v****4,q**** /v****2,q****2**** ratio**
**To test whether the partons in different momentum **
**   ****space also can recombine with each other**

***L.W. Chen, C.M. Ko ******nucl-th 0602025***

*********: modification factor***

## PHENIX in Run 7

***SL Huang QM08***

***PHENIX in Run 7***

***Run 7: ***
-   ~4.5B events and around 50% have been used
-   A new Time of Flight  detector (***TOFw***) has been installed in
-      the west arm of PHENIX
-   A new reaction plane detector (***RxNP***) has been installed in
-     the 38 cm < |z| < 42 cm alone the beam

## TOFw and Aerogel Detectors

***SL Huang QM08***

***TOFw and Aerogel Detectors***

- TOFw  intrinsic timing resolution is ~ 75ps
- /K can be separated to 2.8 GeV/c and K/p can be separated
-      to 4.5 GeV/c
- 3. Together with Aerogel detector(***ACC***), we can identify the K to
-     pT~4 GeV/c  and , p to 7 GeV/c

**Notes:**
M2 unit need change

## Reaction Plane Measurements

***SL Huang QM08***

***RxNP:***
- Two sets of plastic
- scintillators positioned
- on either side of the
- collision vertex
- 12 segments in 
- 2 segments in 
-    1.0 < || < 1.5
-    1.5 < || < 2.8
***BBC:***
-    3.1<||<3.9
- Both  detectors are away from mid-rapidity. Smaller non-flow effect
-     on the reaction plane measurements
- New RxNP detector resolution is around 74% at mid-centrality

***Reaction Plane Measurements***

- Sqrt(2*cos(2*(N-S)))

## Mass ordering of v2 and v4

***S.L. Huang QM08***

***Mass ordering of v******2****** and v******4***

- V4 has been measured as a
- function of pT in different centrality bins for the , K and p
- Mass ordering has been observed for both v2 and v4
***Consistent with the hydrodynamics***
***Poster 166 A.Taranenko***

## KET Scaling of v4

***S.L. Huang QM08***

-  The v4 follows the KET scaling well for KET < 1 GeV
-   The number of constituent  quark scaling holds for v4 when
- KET/nq < 1 GeV. This confirms that matter with partonic degrees
- of freedom has been generated at RHIC

***KE******T ******Scaling of v******4***

***P166  A.Taranenko***

## V4/(v2)2 ratio 

***S.L. Huang QM08***

***V******4******/(v******2******)******2****** ratio ***

-  The ratio of v4/(v2)2 is close to
-     0.9 for the , K and p
-  Mesons and baryons have similar
-     v4/(v2)2 ratio

***What can we extract from ***
***this measurement?***

## Partonic Thermalization !

***S.L. Huang QM08***

***Partonic Thermalization !***

***Parton v******4,q******/(v******2,q******)******2******~0.5     ******Perfect Partonic Liquid!***
***Partons in different momentum space also can ***
***    ******recombine with each other***
***3. Partons interact more frequently and strongly ***
***    ******with each other***

## Charged   v2 

***S.L. Huang QM08***

***Charged ************  v******2****** ***

- Charged  v2 can be measured to
- 6 GeV/c.
- The results are consistent with
- 0 results in the overlap pT region.
-  All  v2 start to drop at pT  ~ 2.5 GeV/c
- in the different centrality bins!

## Kaon and Proton v2 

***SL Huang QM08***

***Kaon and Proton v******2****** ***

- Kaon v2 can be measured to 4 GeV/c and protons v2 can be measured to 6 GeV/c
- Proton v2 starts to drop at pT~ 4 GeV/c

## Break Point? 

***SL Huang QM08***

***Break Point? ***

- In the centrality of 20~60%, the , K and p KET scaling seemly begins to
-     break at KET/nq ~ 1 GeV
- More statistics are required for the further investigation
***                         ******A factor 2 of Run 7 data will come after QM08***

**KE****T****/nq(GeV)**

**KE****T****/nq(GeV)**

## Conclusions 

***SL Huang QM08***

***Conclusions ***

- New time of flight detector(TOFw) of PHENIX runs successfully
- in Run 7 with 75 ps intrinsic timing resolution. With new TOFw and RxNP detectors, we can measure the identified charged hadrons v2 to pT~6 GeV/c and v4 to 3 GeV/c

- The number of constituent  quark scaling has been observed
- for v4 for KET/nq < 1 GeV. Mesons and bayrons have similar
- v4/(v2)2 ratio which is close to 0.9
***The parton v******4,q******/(v******2,q******)******2 ******~ 0.5 : perfect partonic liquid  ***
***Partonic Thermalization***

- The number of constituent quark scaling seemly begins to break for v2 as KET/nq~1GeV at 20~60% centrality:
- a)The interface between hydro and jet fragmentation
- b)Quantitative information about density and interaction strength