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e +. ω. e ー. ω. ω. Low mass vector meson measurements at RHIC Systematic Measurement of omega mesons in PHENIX. π +. π 0. π 0. ー                     ー. γ. Misaki Ouchida Hiroshima University For the PHENIX Collaboration. π ー. γ. γ. γ. γ. OUTLINE. Introduction

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Low mass vector meson measurements at rhic systematic measurement of omega mesons in phenix

e

ω

eー

ω

ω

Low mass vector meson measurements at RHICSystematic Measurement ofomega mesons in PHENIX

π+

π0

π0

ー                     ー

γ

Misaki Ouchida

Hiroshima University

For the PHENIX Collaboration

πー

γ

γ

γ

γ


Outline
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


Introduction why low mass vector mesons
Introduction WhyLow Mass Vector mesons?

  •  e+e- (BR:7x10-3%)

w p0g (BR:9%)

Reconstructed

Efficiency

ωpT

p+p

  • Systematic Study of

  • Low Mass Vector Mesons

  • different decay mode

  • (lepton, hadron)

  • different collision mode

  • (p+p, d+Au, A+A)

Promising probe to

study the properties

of the deconfined state

d+Au

Matter ( life time~10fm/c )

omega meson ( life time 23fm/c )

A+A

phi meson ( life time 46fm/c )

Physics…

Signal for Chiral Symmtery Restoration

Signal for Jet Quenching

Low pT High pT


Suppression as a probe of qgp
Suppression as a Probe of QGP

Introduction WhyLow Mass Vector mesons?

Hadron Production will be suppressed due to the jet quenching occurred in the heavy-ion collisions as an effect of the matter

The inclusive pi0 production in Au+Au

QGP

Nuclear Modification Function

In the absence of nuclear effects: RAA=1

PRL 91. 072301 (2003)


Experiment Which decay mode do we measure ?

γ

γ

π0

π0

γ

γ

e+

π+

e-

ω

ω→π0π+π-

ω→π0γ

γ

γ

φ→e+e-

ω→e+e-

Hadron ID

Energy

Momentum

π-

Momentum

Electron 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.


Analysis highlight how do we approach
Analysis HighlightHowdo we approach?

d+Au

d+Au

w p0g

p+p

p+p, d+Au

collisions

wφ e+e-

wφ e+e-

p+p

w p+p-p0

Both leptonic and

hadronic decay channel are measured


Analysis HighlightHowdo we approach?

Challenge to A+A Collisions

Quest for Low Mass Vector Mesons

in huge huge Background


Analysis highlight how do we approach1
Analysis HighlightHowdo we approach?

Best Cuts

S/√B (significance)

No Cuts

pT(ω) [GeV/c]

Improving S/N

  • Further Cut Optimization

e.g.w p0g @ Au+Au

Kinematical Cuts for Reconstruction

・Transverse Momentum of

・Photon Energy

・Width of Invariant Mass

Rising

Minimum Cuts

Use Best Cuts that improve S/√B (significance) the most


Analysis HighlightHowdo we approach?

BG

BG

Signal

BG

Subtracting Backgrounds ( 2 body:wφ e+e- , φ K+K-)

conbinatorial

backgrounds

w,f→ee

Extract

by Event Mixing

AN 612


Analysis HighlightHowdo we approach?

Subtracting Backgrounds ( 3 body:w p0g(p02g))

Mixed event

w

Reconstructed invariant mass

Peripheral (cent 60~92 %)

3.5<pT<4.5[GeV/c]

BG2

Black: FG

count

BG3

BG1

Magenta:BG1+BG2+BG3

after subtraction of

BG1+BG2+BG3

[GeV/c^2]

Gaussian (Mean and With are Fixed

by Embedding simulation)


Results discussion what do we see
Results & Discussion Whatdo we see?

  • Spectra (p+p & d+Au)


Results discussion what do we see1
Results & Discussion Whatdo we see?

Getting down

in higher centrality

  • Spectra (Au+Au)

w p0g , w e+e-@ Au+Au

Suggesting Hadron suppression


Results & Discussion Whatdo we see?

Interesting systematic measurement of hadron suppression


Results & Discussion Whatdo we see?

Interesting systematic measurement of hadron suppression


Summary
Summary

Physics…

yet to be discussed…

provide intriguing result

Signal for Chiral Symmtery Restoration

Signal for Hadron Suppression

  • PHENIX measured Low Mass Vector Meson, φandω production in both leptonic and hadronic channels in different collision system.

    • Spectra show good agreement among several decay channels in p+p and d+Au

    • A+A results have an ability to discuss hadron suppression providing intriguing systematic results.

Low pT High pT

Systematic measurement of omega in PHENIX will be published in near furture



Results & Discussion Whatdo we see?

w p0g@ Au+Au

  • Nuclear Modification Function: RAA

φ K+K-@ Au+Au

Suggesting Hadron suppression

same as other mesons

Suggesting Hadron suppression

same as other mesons


Results discussion what do we see2
Results & Discussion Whatdo we see?

  • Spectra (A+A)

w p0g , w e+e-@ Au+Au

PHENIX Preliminary & Work In Progress

wφ e+e- , φ K+K- @ Au+Au

PHENIX Preliminary

Suggesting Hadron suppression

same as other mesons


Analysis HighlightHowdo we approach?

Cu+Cu

w p0g

Using detector thresholds

RHIC

EMCal

Chose the data set that only take high pT

 High statistic


Omega Spectra (together)

0-20%

M.B.

20-60%

60-92%



Another Energy Correction

Correct Measured Energy Value to True Energy Value

(Assumed as E1E2 has a true value)

If energy is measured within the energy resolution band (yellow and red band),

shrink it to E1E2 curve.

Minimize Χ2 value= ((E1-E1(measured))/σE1)2 + ((E2-E2(measured))/σE2)2

where E1*E2 = m(pi0PDG)/2(1-cos)

Energy reso.

corrected

uncorrected

Can correct also pT!



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