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 CollaborationJPS meeting, Mar. 2012

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outline

Introduction Motivation Analysis method Current status Summary and Outlook

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What is HBT ? Quantum interference between identical two particles Powerful tool to explore space-time evolution in HI collisions HBT can measure the source size at freeze-out,

Not whole size But homogeneity region in expanding source

21 ppq

detector

detector

1p

2p

ToutTside

T

kqkq

ppk

//,2

21

)exp(1)(~1

)()(),(

222

21

212

invinvqRq

pPpPppPC

P(p1) : Probability of detecting a particle

P(p1,p2) : Probability of detecting pair particles

3

〜 1/R

assuming gaussian source

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Azimuthal HBT measurement “Out-Side-Long” system

Source shape at freeze-out is measured relative to 2nd order event plane Sensitive to “system lifetime”Related to “momentum anistropy”

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Rlong: Longtudinal sizeRside: Transverse sizeRout: Transverse size + emission durationRos: Cross term between Out and Side

R longBeam

Rside

Rout

Beam

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HBT and Triangular flow Can we measure triangularity by HBT ?

Answer by Blast Wave model is “Yes” S.Voloshin at QM2011

Azimuthal HBT relative to Ψ3 will

give us more detailed information of initial conditions and system evolution

Centrality dependence of v3 is very weak unlike v2

How about triangularity at freeze-out ?

5pT[GeV/c]

vn v2

v3

PRL.107, 252301(2011)

Blast wave model calculationby S.Voloshin at QM11

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Analysis method for HBT Correlation function

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 funcyionIncluding the effect of long lived resonance decay

6)2exp(

]1[])1([2222222

222

outsideoslonglongoutoutsideside

halocore

qqRqRqRqRG

FGCCC

Ψ3

R(q): real pairs M(q): mixed pairs q: relative momentum of pair

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Ψ3 dependence for different mixing conditions

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Data: Au+Au 200GeV in PHENIXCharged pion pairs are used

“Ψn” mixing is applied here besides centrality and zvertex

If Ψ3 mixing is not applied,

- oscillation of Rside become strong - oscillation of Rout become weak

if both Ψ2&Ψ3 mixing is applied,

- Similar to Ψ3 mixing

- Is this mixing correct ?→How was Ψ2 dependence ?

Ψ2 mixing

Ψ3 mixing

Ψ2&Ψ3 mixing

side out

0-10%

10-20%

20-30%

30-60%

Δφ=φpair–Ψ3

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How was Ψ2 dependence ?

If Ψ2 mixing is not applied, - oscillation of Rside become strong - oscillation of Rout become weak

Because flow(v2) will be included in mixed pairs for all azimuth angle ?

Similar tendency with Ψ3 analysis

At least, Ψn mixing will be needed to see Ψn dependence

side out

Ψ2 mixing

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without Ψn mixingΔφ=φpair–Ψ2

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Ψ3 dependence for different mixing conditions

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Ψ2 mixing

Ψ3 mixing

Ψ2&Ψ3 mixing

side out Data: Au+Au 200GeV in PHENIX

Pion pairs are used “Ψn” mixing is applied here besides

centrality and zvertex If Ψ3 mixing is not applied,

- oscillation of Rside become strong - oscillation of Rout become weak

if both Ψ2&Ψ3 mixing is applied,

- Similar to Ψ3 mixing

- Is this mixing correct ?

→How was Ψ2 dependence ?

Ψ3 mixing wll be needed Mixed-pairs should be same condition

with Real pairs, so Ψ2 mixing will be also needed

This is still “work in progress”

0-10%

10-20%

20-30%

30-60%

Δφ=φpair–Ψ3

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Ψ2&Ψ3 mixing result is compared vs AMPT

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

vs Blast wave model Different tendency in Rside

But both model says “Need more study”

Comparison with Model

S.Voloshin at QM11

side

out

side out

SideOut

AMPT

Blast wave model

S.Voloshin at QM11T=100[MeV], ρ=r’ρmax(1+cos(nφ)) 10

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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”Further study will be done

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Outlook Need more mixing study Acceptance study is ongoing Any simulation may be needed

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PHENIX Detectors Vertex, Centrality

Vertex, BBC, ZDC

Event planeReaction Plane Detector(RxNP)

TrackingDrift Chamber, Pad Chamber

PID by EMCalUsed all sectors in west arm

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Correlation function for charged pions

Raw C2 for 30-60% centrality Solid lines is fit functions

R.P

R.P

R.P

R.P

1DInv

3DSide Out Long

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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?

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out-of-plane

in-plane