Download - Measurement of the higher order azimuthal anisotropy (v n ) for charged hadrons at RHIC-PHENIX
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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
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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
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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!
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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?
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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)
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John C.-H. Chen 6
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John C.-H. Chen 7
vn(n) vs pT
• All vn increases with pT
• v3 is independent from centrality
PRL 107 252301 (2011)
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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
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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)
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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.
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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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John C.-H. Chen 12
NQS of PID vn
• (vn/nqn/2) KET scaling in all vn
• vn also shown in partonic level
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John C.-H. Chen 13
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
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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
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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?
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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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John C.-H. Chen 1717
PID v2 @ 62.4 and 39 GeV
• NQS scaling still works at 39 GeV!
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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?
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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