1. John Chin-Hao Chen RIKEN Brookhaven Research Center
vn in PHENIX
John Chin-Hao Chen RIKEN Brookhaven Research Center
INT Ridge Workshop 2012/05/08
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(f-y) =N0(S(1+2vncosn(f-y)))
v2 = elliptic flow
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. Fluctuation matters
Nucleon distribution is not smooth, or initial state fluctuation -> finite vodd
Azimuthal symmetry of the colliding area no longer available
vodd is possible
We can “measure” the fluctuations directly
John C.-H. Chen

5. v3, reason for ridge and shoulder?
Ridge sits at Df ~ 0, shoulder sits at Df~2p/3, 4p/3
A 3-peak structure!
v3 (Fourier Coefficient of the cos3Df term) gives a natural 3-peak structure
Is v3 the explanation?
John C.-H. Chen

6. How do we measure vn? Reaction plane method
Use forward detector to determine the n-th reaction plane, Yn
dN/df  1+S2vncos n(f-Yn)
vn = <cos n(f-Yn)>
Two particle correlation method
central-central or central-forward correlation
dNpair/dDf  1+S(2vnAvnBcosnDf)
John C.-H. Chen

7. John C.-H. Chen

8. Reaction plane method vn {Yn} = <cos(n(f-Fnave))> / Res(Yn)
Fnave is the average of the raw reaction plane between north and south sub-events
Res(Yn) is the reaction plane resolution
John C.-H. Chen

9. Correlation factor
Res(Yn), Resolution of reaction plane measures cosine of dispersion of Y estimator (F) from truth
Res(Y2) = <cos(2(Y2(N/S) – YRP))> = sqrt(<cos2(Y2N – Y2S)>)
Key Quantity: cosine of dispersion (Raw vn of YA wrt YB)
<cos j (YmN – YnS)>
John C.-H. Chen

10. Reaction plane correlation (i)
A: RXN North [ ]
B: BBC South [ ]
C: MPC North [ ]
D: MPC South [ ]
PRL (2011)
<cos j (FmA – FnB)>
N-th reaction plane (Fn) correlates across large rapidity (|hA-hB|~5, |hC-hD|~7)
N = 1 (F1) has negative correlation due to conservation of momentum
John C.-H. Chen

11. Reaction plane correlation (II)
A: RXN North [ ]
B: BBC South [ ]
C: MPC North [ ]
D: MPC South [ ]
PRL (2011)
F2 correlates with F1
F2 correlates with F4
F2 does not correlate with F3
F1 correlates negatively with F3,
some intrinsic v3 not coming from fluctuation?
John C.-H. Chen

12. vn(Yn) vs pT All vn increases with pT
PRL (2011)
All vn increases with pT
v3 is independent from centrality
John C.-H. Chen

13. Characterize the initial state anisotropy
Glauber initial state condition
use en to measure the initial state anisotropy
John C.-H. Chen

14. vn vs en vn follows the trend of en
Initial state anisotropy translate to final state momentum anisotropy
John C.-H. Chen

15. v3(2p) vs v3(Y3)
v3 measured by two particle correlation method (0.3<|Dh|<0.7) is consistent with, but slightly higher than the reaction plane method
Contributions from non-flow (jet contribution) in this Dh range
John C.-H. Chen

16. vn vs theory All theory predicts v2 well
v3 adds in additional discrimination power
Data favors Glauber + h/s = 1/4p
PRL (2011)
John C.-H. Chen

17. Jet shape with higher vn modulated background subtraction
200GeV Au+Au
0-20%, inc. g-had.
When v3 modulation is included, the double peak structure in away-side disappears.
John C.-H. Chen

18. v2 of Identified particles
v2 of identified particles are measured
(v2/nq) are the same for all particles
Flow exists at partonic level
John C.-H. Chen

19. High pT PID v2 new detector TOFw and Aerogel enhance PID capability
arxiv:
new detector TOFw and Aerogel enhance PID capability
Dedicated reaction plane detector
Extend to high pT
John C.-H. Chen

20. NQS breaks? NQS holds at 0-20%
arxiv:
NQS holds at 0-20%
Obviously breaks at 20-60% at KET/nq > 1.0 GeV
John C.-H. Chen

21. 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:
John C.-H. Chen

22. PID v3 @ 200 GeV Au+Au Mass ordering at low pT
Baryon/meson splitting at intermediate pT
John C.-H. Chen

23. NQS of PID v3 Similar (v3/nq) scaling exists in v3
v3 also shown in partonic level
John C.-H. Chen

24. 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

25. vn{yn} at 39 GeV Inclusive charged hadrons
Significant values of v3 and v4
Trend similar to vn at 200 GeV
John C.-H. Chen

26. Beam energy dependence of vn
Various beam energy: 39, 62, 200 GeV
No significant beam energy dependence
Hydro dynamical behavior down to 39 GeV
John C.-H. Chen

27. PID v2 @ 62.4 and 39 GeV NQS scaling still works at 39 GeV!
John C.-H. Chen 27

28. 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

29. Saturation function of vn
Not only v2 is saturated, but also the v3 and v4, starting from 39 GeV
John C.-H. Chen

30. 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 GeV
But the KET/nq scaling breaks at large KET/nq in mid-central collisions
John C.-H. Chen