Azimuthal HBT measurement of charged pions
With respect to 3rd event plane
In Au+Au 200GeV collisions at RHIC-PHENIX
Takafumi Niida for the PHENIX Collaboration
JPS meeting, Mar. 2012
outline
 Introduction
 Motivation
T . Niida
 Summary and Outlook
2
 Current status
JPS Mar. 2012
 Analysis method
What is HBT ?
 Quantum interference between identical two particles
 Powerful tool to explore space-time evolution in HI collisions
〜1/R
JPS Mar. 2012
assuming gaussian source

p1
detector

p2
detector
3
P(p1) : Probability of detecting a particle
P(p1,p2) : Probability of detecting pair particles
  
q  p1  p2



p1  p 2
kT 
2




q side  kT , qout // kT
T . Niida
 HBT can measure the source size at freeze-out,
Not whole size But homogeneity region in expanding source
Azimuthal HBT measurement
 “Out-Side-Long” system
2
2
C2 =1+ l exp(-Rinv
qinv
)
2
2
2
2
2
2
=1+ l exp(-Rside
qside
- Rout
qout
- Rlong
qlong
- 2Ros2 qside qout )
Rside
Sensitive to “system lifetime”
Related to “momentum anistropy”
Beam
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 Source shape at freeze-out is measured relative to 2nd order event plane
JPS Mar. 2012
Rout
4
Rlong: Longtudinal size
Rside: Transverse size
Rout: Transverse size + emission duration
Ros: Cross term between Out and Side
HBT and Triangular flow
 Can we measure triangularity by HBT ?
 Answer by Blast Wave model is “Yes”
 S.Voloshin at QM2011
Y3
Y2
 Azimuthal HBT relative to Ψ3 will
initial conditions and system evolution
vn
PRL.107, 252301(2011)
v2
T . Niida
 How about triangularity at freeze-out ?
v3
pT[GeV/c]
5
 Centrality dependence of v3 is very weak unlike v2
Blast wave model calculation
by S.Voloshin at QM11
JPS Mar. 2012
give us more detailed information of
Analysis method for HBT
 Correlation function
R(q): real pairs
M(q): mixed pairs
3 directions of Ψ3 are not distinguished
Mixed pairs are made by event mixing
 Events with similar centrality, zvertex, Ψ2 are used
 In this analysis, Should we consider Ψ3 for mixed pairs?
 Correction of event plane resolution (U.Heinz et al, PRC66, 044903 (2002))
 Coulomb correction by Sinykov‘s fit funcyion
Including the effect of long lived resonance decay
Ψ3
JPS Mar. 2012
q: relative momentum of pair
T . Niida
R(q)
C2 =
M (q)
C 2  C 2core  C 2halo
2
2
2
2
2
2
G  exp( Rside
q side
 Rout
qout
 Rlong
qlong
 2 Ros2 q side qout )
6
 [ (1  G ) F ]  [1   ]
Ψ3 dependence for different mixing conditions
side
 Data: Au+Au 200GeV in PHENIX
 if both Ψ2&Ψ3 mixing is applied,
10-20%
20-30%
30-60%
Ψ2 mixing
JPS Mar. 2012
- oscillation of Rside become strong
- oscillation of Rout become weak
0-10%
Δφ=φpair–Ψ3
- Similar to Ψ3 mixing
- Is this mixing correct ?
→How was Ψ2 dependence ?
Ψ2&Ψ3 mixing
T . Niida
 If Ψ3 mixing is not applied,
Ψ3 mixing
7
Charged pion pairs are used
 “Ψn” mixing is applied here besides
centrality and zvertex
out
How was Ψ2 dependence ?
Ψ2 mixing
 If Ψ2 mixing is not applied,
- oscillation of Rside become strong
- oscillation of Rout become weak
JPS Mar. 2012
Because flow(v2) will be included in
mixed pairs for all azimuth angle ?
 Similar tendency with Ψ3 analysis
T . Niida
 At least, Ψn mixing will be needed
to see Ψn dependence
without Ψn mixing
out
Δφ=φpair–Ψ2
8
side
Ψ3 dependence for different mixing conditions
side
 Data: Au+Au 200GeV in PHENIX
Ψ3 mixing
Pion pairs are used
 “Ψn” mixing is applied here besides
centrality and zvertex
10-20%
 If Ψ3 mixing is not applied,
20-30%
0-10%
30-60%
- oscillation of Rside become strong
- oscillation of Rout become weak
JPS Mar. 2012
Ψ2 mixing
Δφ=φpair–Ψ3
- Similar to Ψ3 mixing
- Is this mixing correct ?
→How was Ψ2 dependence ?
 Ψ3 mixing wll be needed
Ψ2&Ψ3 mixing
T . Niida
 if both Ψ2&Ψ3 mixing is applied,
out
 This is still “work in progress”
9
 Mixed-pairs should be same condition
with Real pairs, so Ψ2 mixing will be also needed
Comparison with Model
 Ψ2&Ψ3 mixing result is compared
 vs AMPT
AMPT S.Voloshin at QM11
 n=2 Rs and Ro have the opposite sign in oscillation
 n=3 Rs and Ro have the same sign in oscillation
 Same tendency with current result
out
side
T . Niida
Blast wave model
 vs Blast wave model
Side
 Different tendency in Rside
But both model says “Need more study” Out
S.Voloshin at QM11
T=100[MeV], ρ=r’ρmax(1+cos(nφ))
10

JPS Mar. 2012
side
out
Summary
 Azimuthal HBT measurement w.r.t Ψ3 is in progress
 Tendency of Rside and Rout oscillation changes by Ψn mixing conditions.
 Ψ2 and Ψ3 mixing will be needed to see “Ψ3” dependence of HBT radii
 Current result is similar to AMPT, and different from Blast wave model.
 This is still ”work in progress”
 Need more mixing study
 Acceptance study is ongoing
T . Niida
Outlook
JPS Mar. 2012
Further study will be done
11
 Any simulation may be needed
12
T . Niida
JPS Mar. 2012
Back up
PHENIX Detectors
 Vertex, Centrality
Vertex,
BBC, ZDC
 Event plane
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Used all sectors in west arm
13
Drift Chamber, Pad Chamber
 PID by EMCal
JPS Mar. 2012
Reaction Plane Detector(RxNP)
 Tracking
3D
Correlation function for1D
charged
Out
Inv
Side pions
Long
R.P
 Raw C2 for 30-60% centrality
 Solid lines is fit functions
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R.P
JPS Mar. 2012
R.P
14
R.P
Azimuthal HBT radii for pions
 Observed oscillation for Rside, Rout, Ros
 Rout in 0-10% has oscillation
 Different emission duration between in-plane and out-of-plane?
15
in-plane
T . Niida
JPS Mar. 2012
out-of-plane