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

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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)


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

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


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

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


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

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


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

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


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

Results & Discussion Whatdo we see?

Interesting systematic measurement of hadron suppression


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

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


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

Back up


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

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


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

Analysis HighlightHowdo we approach?

Cu+Cu

w p0g

Using detector thresholds

RHIC

EMCal

Chose the data set that only take high pT

 High statistic


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

Omega Spectra (together)

0-20%

M.B.

20-60%

60-92%


Phenix

PHENIX


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

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!


D au results

d+Au results


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