John C.-H. Chen 1

Measurement of the higher order azimuthal anisotropy (vn) for charged

hadrons at RHIC-PHENIX

John Chin-Hao Chen for PHENIX collaborationRIKEN Brookhaven Research Center

NN20122012/05/31

John C.-H. Chen 2

vn: particle anisotropy• The colliding area is

“almond” like shape due to overlap of two colliding nuclei.

• The particle angular distribution: dN/d(-) =N0((1+2vncosn(-n)))

• Nucleon distribution is not smooth, or initial state fluctuation -> finite vodd

• We can “measure” the fluctuations directly

John C.-H. Chen 3

Many information coming from flow

• Equation of State (EOS)• shear viscosity (η),• specific viscosity (η/s) of

sQGP • and their temperature

dependence

• Key to understand the QGP!

John C.-H. Chen 4

v3, reason for ridge and shoulder?

• Ridge sits at ~ 0, shoulder sits at ~2/3, 4/3– A 3-peak structure!

• v3 (Fourier Coefficient of the cos3term) gives a natural 3-peak structure

• Is v3 the explanation?

John C.-H. Chen 5

How do we measure vn?

• Reaction plane method– Use forward detector to determine the n-th

reaction plane, n

– dN/d 1+2vncos n(-n)– vn = <cos n(-n)>

• Two particle correlation method– central-central or central-forward correlation– dNpair/d 1+(2vn

AvnBcosn)

John C.-H. Chen 6

John C.-H. Chen 7

vn(n) vs pT

• All vn increases with pT

• v3 is independent from centrality

PRL 107 252301 (2011)

John C.-H. Chen 8

vn vs geometrical anisotropy

• Use n to describe geometrical anisotropy

• vn follows the trend of n

• Initial state anisotropy translate to final state momentum anisotropy

John C.-H. Chen 9

vn vs theory

• All theories describe v2 well

• v3 adds in additional discrimination power

• Data favors Glauber + /s = 1/4

PRL 107 252301 (2011)

John C.-H. Chen 10

Jet shape with higher vn modulated background subtraction

• When v3 modulation is included, the double peak structure in away-side disappears.

200GeV Au+Au0-20%, inc. -had.

John C.-H. Chen 11

PID vn @ 200 GeV Au+Au

• Mass ordering at low pT

• Baryon/meson splitting at intermediate pT

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NQS of PID vn

• (vn/nqn/2) KET scaling in all vn

• vn also shown in partonic level

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PID v2 in higher pT

• new detector TOFw and Aerogel enhance PID capability

• Dedicated reaction plane detector• Extend to high pT (6 GeV/c)

arxiv:1203.2644

John C.-H. Chen 14

KET/nq scaling vs centrality

• With finer centrality bins, the centrality dependence is clear

• KET/nq scaling works at 0-10%

• It starts breaking at 10-20% at KET/nq~ 1.0 GeV

arxiv:1203.2644

John C.-H. Chen 15

QCD phase transition

• QGP is created at RHIC at 200 GeV

• RHIC is flexible in beam energy– Down to 7.7 GeV

• Can we find the critical point?– Any significant

feature?

John C.-H. Chen 16

Beam energy dependence of vn

• Various beam energy: 39, 62, 200 GeV• No significant beam energy dependence• Hydro dynamical behavior down to 39 GeV

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PID v2 @ 62.4 and 39 GeV

• NQS scaling still works at 39 GeV!

John C.-H. Chen 18

v2 measurement in broad energy range

• At 7.7 GeV, the v2 value is significantly lower than 200 GeV• A possible transition between 7.7 and 39 GeV?

John C.-H. Chen 19

summary

• vn has been measured systematically in PHENIX

• vn is independent from beam energy between 39 GeV to 200 GeV

• KET/nq scaling work on PID v2 from 39-200 GeV

• But the KET/nq scaling breaks at large KET/nq in mid-central collisions