2.Η ιστορία της εκ. και η μελέτη της Βασιλική Δημοσθένους ΝΙΚΟΛΑΪΔΕΙΟ Γ. Π.
2008 Oct. ATHIC @ Tsukuba 1 Misaki Ouchida Hiroshima University For the PHENIX Collaboration ω ω...
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Transcript of 2008 Oct. ATHIC @ Tsukuba 1 Misaki Ouchida Hiroshima University For the PHENIX Collaboration ω ω...
1
2008 Oct. ATHIC @ Tsukuba
Misaki Ouchida Hiroshima University For the PHENIX Collaboration
ωωω
e +
e ー
γ
γ
π+π0
γ
π ーπ0
γ γ
Low mass vector meson measurements at RHIC
Systematic Measurement ofomega mesons in PHENIX
ー ーー ー
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
OUTLINE
• Introduction Why Low Mass Vector mesons ?
• Experiment Which decay mode do we measure in PHENIX?
• Analysis Highlight How do we approach?
• Results & Discussion What do we see?
• Summary
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Introduction Why Low Mass Vector mesons?
Physics…
Low pT High pT
Signal for Chiral Symmtery Restoration
p+p
d+ Au
A+ A
Systematic Study of Low Mass Vector Mesons
-different decay mode(lepton, hadron)-different collision mode(p+p, d+Au, A+A) Matter ( life time~10fm/c )
omega meson ( life time 23fm/c )
phi meson ( life time 46fm/c )
Promising probe to study the properties of the deconfined state
Rec
on
stru
cted
Rec
on
stru
cted
Eff
icie
ncy
Eff
icie
ncy
e+e- (BR:7x10-3%)
(BR:9%)
ωpTωpT
Signal for Jet Quenching
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Suppression as a Probe of QGP
PRL 91. 072301 (2003)
)/(
/
Tpp
AB
TAA
AA dydpdT
dydpdR
Nuclear Modification Function
QGP
In the absence of nuclear effects: RAA=1
The inclusive pi0 production in Au+Au
Hadron Production will be suppressed due to the jet quenching occurred in the heavy-ion collisions as an effect of the matter
Introduction Why Low Mass Vector mesons?
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
e+
e-
Momentum Electron ID
π-
φ→e+e-
ω→e+e-
π+
ω
γ
γπ0
γγ
γ
γ
π0
ω→π0π+π-
ω→π0γ
EnergyMomentum Hadron ID
PHENIX spectrometer<Global detector>• BBC & ZDC : Event trigger, Collision vertex, Centrality <Central arm>• Acceptance ⇒ pseud-rapidity range : |η| < 0.35 azimuthal angle : 2x90 degree• DC & PC : tracking, momentum• RICH & EMC : electron ID• TOF, EMC : hadron ID<Muon arm>• MuID : muon ID
⇒PHENIX consists of multi-purpose detector to measure rare probe from collisons.
Experiment Which decay mode do we measure ?
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
p+p, d+Aucollisions
Analysis Highlight How do we approach?p+p d+ Au
d+ Au
φ e+e- φ e+e-
+-
p+p
Both leptonic andhadronic decay channel are measured
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Quest for Low Mass Vector Mesons in huge huge Background
Analysis Highlight How do we approach?
Challenge to A+A Collisions
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Analysis Highlight How do we approach?
Improving S/N
pT(ω) [GeV/c]
S/√
B (
sig
nif
ican
ce)
No Cuts
Best Cuts
• Cut Optimization e.g. @ Au+Au
Kinematical Cuts for Reconstruction
・ Transverse Momentum of ・ Photon Energy・Width of Invariant Mass
0 Rising Minimum Cuts
Use Best Cuts that improve S/√B (significance) the most
0
p[GeV/cp[GeV/c22] E[GeV] MassWidth] E[GeV] MassWidth
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Analysis Highlight How do we approach?
Subtracting Backgrounds ( 2 body: φ e+e-φ K+K- )
φBG
BG
conbinatorial backgrounds
Extract by Event Mixing
→ee
BGSignalSignal
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Black: FG
[GeV/c^2]
Peripheral (cent 60~92 %)3.5<pT<4.5[GeV/c]
Magenta:BG1+BG2+BG3 BG3
BG2
BG1
Gaussian (Mean and With are Fixed by Embedding simulation)
after subtraction of
BG1+BG2+BG3
coun
t
Reconstructed invariant mass
Mixed event
0sK
Analysis Highlight How do we approach?
Subtracting Backgrounds ( 3 body: ( 2)
BG1 BG2
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
• Spectra (p+p & d+Au)
Results & Discussion What do we see?
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
• Spectra (Au+Au) , e+e- @ Au+Au
Results & Discussion What do we see?
Suggesting Hadron suppression
Get
tin
g d
ow
n
Get
tin
g d
ow
n
in h
igh
er c
entr
alit
y
in h
igh
er c
entr
alit
y
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Results & Discussion What do we see?
Interesting systematic measurement of hadron suppression
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Results & Discussion What do we see?
Interesting systematic measurement of hadron suppression
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Summary
• PHENIX measured Low Mass Vector Meson, φandω production in both leptonic and hadronic channels in different collision system.– Spectra show good agreement among several deca
y channels in p+p and d+Au– A+A results have an ability to discuss hadron suppr
ession providing intriguing systematic results.
Physics…
Low pT High pT
Signal for Chiral Symmtery Restoration
Signal for Hadron Suppression
yet to be discussed…provide intriguing result
Systematic measurement of omega in PHENIX will be published in near furtureSystematic measurement of omega in PHENIX will be published in near furture
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Back upBack up
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Chiral Symmetry Restoration
Chiral symmetry is restored<qq> → 0
Chiral symmetry is spontaneously broken <qq>~250 MeV
ー
3ー
(Heavy Ion Collider used for this study)
Phys.Rev.Lett.55(1985)158.Nucl.Phys.A443(1993)59c.
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Prediction of theory
T.Hatsuda and S.H.LeeP.R.C.46(1992)R34 →
R.Rapp,H.Hees and T.Stronghep-ph/0611339 ↓
There’s no clear consistent results for the theoritical approach to search for the effect of Chiral Symmetry Restoration.
This is the example where experiments has the potential to guide the theory!
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Phi results
φ K+K- @ Au+Au
φ e+e-φ K+K- @ Au+Au
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
d+Au results (omega)
@ d+Au
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
STAR results
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
RAA with direct photon
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Cut Optimization
・ Pi0 Momentum Cuts・ Photon Energy Cuts・ Pi0 Mass Width
Great influence on the peak significancePi0 Momentum
CutsPhoton Energy Cut
Pi0 Mass Width
Default
Cut#1
Cut#2
Cut#3
Cut#4
S/√B
ex. 4.5<ωpT<5.5 (GeV/c)
If there’s no cut, S/B< 1/1000….→Have to improve it by the selection
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Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Estimation of omega cross-section