Low mass vector meson measurements at RHIC Systematic Measurement of omega mesons in PHENIX

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

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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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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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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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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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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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• 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