Transcript "v n in PHENIX"

vn in PHENIX
John Chin-Hao Chen
RIKEN Brookhaven Research Center
INT Ridge Workshop
2012/05/08
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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(fy)))
• v2 = elliptic flow
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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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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
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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?
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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)
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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
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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)>
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Reaction plane correlation (i)
A: RXN North [1.0-2.8]
B: BBC South [3.1-3.9]
C: MPC North [3.1-3.7]
D: MPC South [3.1-3.7]
PRL 107 252301 (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
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Reaction plane correlation (II)
A: RXN North [1.0-2.8]
B: BBC South [3.1-3.9]
C: MPC North [3.1-3.7]
D: MPC South [3.1-3.7]
• F2 correlates with F1
• F2 correlates with F4
• F2 does not correlate with F3
• F1 correlates negatively with F3,
PRL 107 252301 (2011)
– some intrinsic v3 not coming from fluctuation?
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vn(Yn) vs pT
PRL 107 252301 (2011)
• All vn increases with pT
• v3 is independent from centrality
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Characterize the initial state anisotropy
• Glauber initial state
condition
• use en to measure
the initial state
anisotropy
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vn vs en
• vn follows the trend of en
• Initial state anisotropy translate to final state
momentum anisotropy
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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
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vn vs theory
PRL 107 252301 (2011)
• All theory predicts v2 well
• v3 adds in additional discrimination power
• Data favors Glauber + h/s = 1/4p
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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.
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v2 of Identified particles
• v2 of identified particles are measured
• (v2/nq) are the same for all particles
– Flow exists at partonic level
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High pT PID v2
arxiv:1203.2644
• new detector TOFw and Aerogel enhance PID capability
• Dedicated reaction plane detector
• Extend to high pT
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NQS breaks?
arxiv:1203.2644
• NQS holds at 0-20%
• Obviously breaks at 20-60% at KET/nq > 1.0 GeV
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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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PID v3 @ 200 GeV Au+Au
• Mass ordering at low pT
• Baryon/meson splitting at intermediate pT
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NQS of PID v3
• Similar (v3/nq) scaling exists in v3
• v3 also shown in partonic level
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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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vn{yn} at 39 GeV
• Inclusive charged hadrons
• Significant values of v3 and v4
• Trend similar to vn at 200 GeV
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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!
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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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Saturation function of vn
• Not only v2 is saturated, but also the v3 and v4,
starting from 39 GeV
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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
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