イオン衝突実験による高エネルギー重高エネルギー重イオン衝突実験による測定
直接光子の楕円的方位角異方性の直接光子の楕円的方位角異方性の測定( Measurement of π0 and direct photon v2in √sNN = 200GeV Au+Au collision at RHIC-PHENIX )The Physical Society of Japan 61th Annual Meeting

Kentaro MIKI for the PHENIX collaboration
University of Tsukuba
27 Mar 2006

1-1. Introduction ~ probe of QGP ~Quark Gluon Plasma

Studying the QGP state by
Relativistic Heavy Ion Collider.
difficulty of QGP study
probe of initial state of collision

1. We can not see QGP directly
2. large back groundphoton
Photon doesn’t interact with any other hadrons
and they keep their conditions
when they are generated in final state.

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1-2. Introduction ~ direct photon~

prompt photon

thermal photon

photon form
jet fragmentation

direct photon

hadron decay

inclusive photon
Example of direct photon analysis :measurement of RAA
RAA =(1/Nevt)d2N AA/dpTdη
(<Ncoll>/σ NNinel)d2σ NN/dpTdη

We estimate the elliptic flow (v2) ofdirect photon to study initial state of collisions.
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2-1. Motivation ~ elliptic flow of direct photon ~Expectation of photon v2 at relativistic heavy ion collisions

Inclusive photon
hadron decay

Direct photon

thermal photon v2>0
prompt photon v2=0

prompt photon

Thermal photon

annihilation
compton scattering

photon from jet fragmentation
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Bremsstrahlung(energy loss)
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2-2. RHIC-PHENIX
RHIC
The Relativistic Heavy Ion
Collider (RHIC) at Brookhaven
National Laboratory is a worldclass scientific research facility
that began operation in 2000,
following 10 years ofdevelopment and construction.
lead scintillator (PbSc)
・energy resolution
2.1 ⊕ 8.1 %/ E1/2 [GeV]|η| < 0.375

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lead glass (PbGl)
・energy resolution
0.76 ⊕ 5.95 %/ E1/2 [GeV]∆φ=90°×2

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3-1. method of calculation
inclusive photon
direct photon
neutral hadron which havedecay mode to photon (π0,η,…)hadron decay photon

Ex. π0 and inclusive photon v2

work in progressv2

dir . photon

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R * v2 inc . photon − v2 BG _ photon=R −1
Kentaro MIKI

N inc. photon
R = BG _ photon
N6

3-2. calculation of π0 v2calculation step of π 0 v 2Energy cut (Ecore >0.2 GeV)
shower shape cut (χ 2 < 3)photon ID by EMCal

EMCal TOF ( TOF < 1.2 ns)
charged veto ( pc3hit > 6.5 cm)

π0 PID → invariant massazimuthal distribution of π0

fitting by N0[1+2v2cos{2(φ-Ψ)}]1.0~3.0

3.0~5.0

5.0~10.0

correction by reaction
plane resolution
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4-1. result ~ π0 v2 ~

estimate the π0 v2work in progress
hadron decay simulation

estimate the inclusive photon v2

direct photon v2We estimate the π0 v2 more than 1 GeV pT region (work in progress).
This plot compared to charged hadron v2 (PHENIX preliminary)and run 2 result.
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4-2. result ~ hadron (π0 or η) decay photon v2 ~

estimate the π0 v2work in progress
hadron decay simulation

estimate the inclusive photon v2

direct photon v2

This plot shows the hadron (π0 or η) decay photon from π0 or Kaon v2.
Input of π0 decay photon is fitting function of π0 v2.
Input of η decay photon is Kaon v2 (PHENIX preliminary).
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4-3. result ~ inclusive photon v2 ~

estimate the π0 v2work in progress
hadron decay simulation

estimate the inclusive photon v2

direct photon v2

We calculate the inclusive photon and compared to results of previous analysis.

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4-4. result ~ subtract the hadron decay ~work in progress

estimate the π0 v2hadron decay simulation

estimate the inclusive photon v2

R: 00 – 92 %direct photon v2
R =inc . photon

NN BG _ photon

This plot shows v2 of subtracted the hadron decay photon from inclusivephoton.
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4-5. result ~ centrality dependence ~work in progress

These plots show centrality dependence of subtracted photon v2.
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5. summary and to do list
summary+ We estimate v2 of π0, inclusive photon, and subtracted photon
to study initial state of relativistic heavy ion collisions and QGP.
+ We used Au+Au collisions data set in √s NN = 200GeV
at RHIC-PHENIX.
+ Compared to results of previous analysis.
+ We show the subtract photon at less than 5 GeV pT region, andthese results are still work in progress.
to do+ need to more study about systematical error.
+ study of v2 calculation methods+ estimate the direct photon v2 from inclusive photon andhadron decay photon.
+ prepare to show result at more large pT range.

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Ex. Back up

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Ex. Introduction (generation of photon)
Typical generation of photon at heave ion collisions
prompt photon

thermal photon

photon form
jet fragmentation

hadron decay

Photons from compton scattering between
quark and gluon in initial state of collisions.
Photons generated by hadron decay,
too. pi0 or
eta generated
annihilation
comptonscattering
To see the initial stateused by photon,from hottest matter after it expanded and cool down.
we need identified these photons.
When studying QGP by photon, these photons are back ground.
Photons from thermal equilibrium state.
These
photonscattering
have thermal information of initial state.
comptonAnd, these photons are important of studying expansion process about hottest matter.
bremsstrahlung
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Ex. Introduction ~ elliptic flow ~直接光子の楕円的方位角異方性を測る
衝突初期の反応関与部の幾何学的異方性が粒子の運動量空間における異方性に反映される

楕円的方位角異方性 (v2)粒子の生成過程を探る上で重要な情報源z

φ : 発生粒子の方位角
Ψ : reaction planeの方位角x反応平面法(reaction plane)
ビーム軸方向とインパクトパラメータ方向が張る平面
yout plane

例：
荷電ハドロンのv2

reactionplane
in plane
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Ex. systematical error propagate
direct photon
systematic error
hadron decay
photon error

pi0 PID
η contamination
reaction plane determination

reaction plane determination

inclusive
photon error

calculation method difference
reaction plane determination
R=N(inc.)/N(BG.)
error

π0 PID

there are same
componentfrom PPG042
they have to remove
when error propagate of
direct photon
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calculation method of
inclusive photon

17Ex. R

20 to 30 %30 to 40 %20 to 40 %40 to 50 %50 to 60 %40 to 60 %00 to 92 %27/Mar/2006

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Ex. systematical error propagate
hadron decay
photon error

inclusive
photon error

method 1
average

R=N(inc.)/N(BG.)
errordifference ofplot by method 1
and average plot
ratio

method 2

As systematic error of inclusive photon,
I have estimated error from calculation
method difference and reaction planedetermination. The error from photon
PID have not estimated yet.

error fromdifference of calculation method
reaction plane determination

Please refer to my analysis note forcalculation method .
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