Measurement of v2 and v4 in Au+Au

Collisions at different beam energy

from PHENIX

Shengli Huang

for PHENIX Collaboration

Vanderbilt University

Outline

1. Physics motivations

2. The analysis methods

3. The v2 measurements from PHENIX

4. The v4 measurements from PHENIX

5. Summary and Outlooks

2S. HuangWWND2011,Colorado

Physics motivation (1)

S. Huang 3

M. Luzum, J-Y Ollitrault, Phys.Rev.C82:014906,2010

RHIC data indicates the

partonic collectivity has been

generated at RHIC.

Viscous hydro-dynamics

calculations with a small

value of η/s is compatible

with v2 measurements

Beam energy scan will search

for the collision energy where

the partonic matter starts to

turn off

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η/s = 0.08 CGC η/s = 0.16 Glauber

Physics motivation (2)

4S. Huang

The differential v2 saturates at RHIC energy from 62.4 GeV to 200 GeV

Softening of equation of

state

Locate the collision energy for the critical point searching

To measure the v2 and v4 in same rapidity for the same collision system will supply better information for extracting collision energy dependence

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

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Physics motivation (3)

S. Huang 5

v4/v22 is sensitive to the η/s and the freez-out

temperatureSimultaneous measurements of differential v2

and v4 are important for extraction of transport

propertiesGombeaud & J-Y.Ollitrault, PRC 81,014901(2010)

Luzum, &,J-Y. Ollitrault, PRC 81,054910(2010)

Phys. Rev. Lett. 105, 062301 (2010)

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PHENIX Detectors for Event Plane

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Large η gap away central arm |η|<0.35 Systematic study the non-flow effect for

the measurement of v2 and v4

Event plane detectors:Reaction plane detector

RXNIN (1.5<||<2.8)

RXNOUT (1.0<||<1.5)

Muon position EMCal

MPC (3.1<||<3.9)

Beam-beam counter

BBC (3.1<||<3.9)

The event plane Resolution

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σRP for v2, Au+Au at 7.7 GeV

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Robust Measurements

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The measurements from different event plane detectors are

consistent quite wellWWND2011,Colorado

The Energy dependence of v2 (1)

S. Huang 9

There is no energy dependence of v2(pT) for collision energy from 39 GeV

to 200 GeV for different collision centrality bins

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The Energy dependence of v2 (2)

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The v2 at 7.7 GeV Au+Au is much lower than v2 of 39 GeV,

62.4 GeV and 200 GeV

Partonic flow -- Hadronic flow ?

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The Baryon contribution

S. Huang 11

Proton yield dominates in the

positive hadrons, while pion yield

dominates in the negative hadrons

The v2 of negative hadron at 7.7 GeV

Au+Au is lower than v2 of pion at 200

GeV AuAu

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The Energy dependence of v4 (1)

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Similar to v2, the v4 does not show energy dependence

for collision energy from 39 GeV to 200 GeV WWND2011,Colorado

The Energy dependence of v4 (2)

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At mid-centrality, the v4/v22 is around 0.8 as a function of pT in

Au+Au collision from energy 39 GeV to 200 GeV

The v4/v22 is similar from 39 GeV to 200 GeV at different Npart in

Au+Au collisionsWWND2011,Colorado

Summary and outlooks 1. The v2 measurement from PHENIX further indicates that the

v2 saturates from 39 GeV to 200 GeV, but larger than the v2 of

7.7 GeV in AuAu collision

2. The v4 also saturates from 200 GeV to 39 GeV and the

v4/v22 is almost constant from 39 GeV to 200 GeV

3. These results will supply new information for comparison

with results from viscous hydro-dynamics models. It will also

shed light on the path for further research on the critical point

4. The PID v2 and v4 results from PHENIX will be out soon

S. Huang 14WWND2011,Colorado