Measurements of Light Vector Mesons through the e + e - Channel at the PHENIX
Low mass vector meson measurements at RHIC Systematic Measurement of omega mesons in PHENIX
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Transcript of Low mass vector meson measurements at RHIC Systematic Measurement of omega mesons in PHENIX
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12008 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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2 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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3 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
onst
ruct
edR
econ
stru
cted
Effi
cien
cyEf
ficie
ncy
e+e- (BR:7x10-3%)
(BR:9%)
ωpTωpT
Signal for Jet Quenching
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4 Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Suppression as a Probe of QGP
PRL 91. 072301 (2003)
)/(/
Tpp
AB
TAA
AA dydpdTdydpdR
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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5 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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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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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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Analysis Highlight How do we approach?Improving S/N
pT(ω) [GeV/c]S/√B
(sig
nific
ance
)
No Cuts
Best Cuts
• Further Cut Optimizatione.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
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Analysis Highlight How do we approach?
AN 612
Subtracting Backgrounds ( 2 body: φ e+e-φ K+K- )
φBG
BG
conbinatorial backgrounds
Extract by Event Mixing
→ee
BGSignalSignal
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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 ofBG1+BG2+BG3
coun
t
Reconstructed invariant mass
Mixed event
0sK
Analysis Highlight How do we approach?Subtracting Backgrounds ( 3 body: ( 2)
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• Spectra (p+p & d+Au)Results & Discussion What do we see?
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• Spectra (Au+Au) , e+e- @ Au+Au
Results & Discussion What do we see?
Suggesting Hadron suppression
Get
ting
dow
n G
ettin
g do
wn
in h
ighe
r cen
tralit
y
in h
ighe
r cen
tralit
y
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Results & Discussion What do we see?Interesting systematic measurement of hadron suppression
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14 Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
Results & Discussion What do we see?Interesting systematic measurement of hadron suppression
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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 RestorationSignal 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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Back upBack up
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• Nuclear Modification Function: RAA
@ Au+Au
Results & Discussion What do we see?
φ K+K- @ Au+Au
Suggesting Hadron suppression same as other mesonsSuggesting Hadron suppression same as other mesons
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18 Misaki Ouchida2008 Oct. ATHIC @ Tsukuba
• Spectra (A+A) , e+e- @ Au+Au
φ e+e-φ K+K- @ Au+Au
Results & Discussion What do we see?
Suggesting Hadron suppression same as other mesons
PHENIX Preliminary
PHENIX Preliminary & Work In Progress
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Analysis Highlight How do we approach?
Cu+ Cu
RHIC
Chose the data set that only take high pT High statistic
EMCal
Using detector thresholds
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0-20%
20-60%60-92%
M.B.
Omega Spectra (together)
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PHENIX
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Minimize Χ2 value= ((E1-E1(measured))/σE1)2 + ((E2-E2(measured))/σE2)2
Correct Measured Energy Value to True Energy Value (Assumed as E1E2 has a true value)
Can correct also pT!
uncorrected
correctedEnergy reso.
If energy is measured within the energy resolution band (yellow and red band),shrink it to E1E2 curve.
where E1*E2 = m(pi0PDG)/2(1-cos)
Another Energy Correction
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d+Au results