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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 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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  1. 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

  2. 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

  3. 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

  4. 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)

  5. 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.

  6. 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

  7. Analysis HighlightHowdo we approach? Challenge to A+A Collisions Quest for Low Mass Vector Mesons in huge huge Background

  8. Analysis HighlightHowdo we approach? Best Cuts S/√B (significance) No Cuts pT(ω) [GeV/c] Improving S/N • 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 p[GeV/c2] E[GeV] MassWidth

  9. Analysis HighlightHowdo we approach? BG BG Signal BG wφ Subtracting Backgrounds ( 2 body:wφ e+e- , φ K+K-) conbinatorial backgrounds w,f→ee Extract by Event Mixing

  10. Analysis HighlightHowdo we approach? Subtracting Backgrounds ( 3 body:w p0g(p02g)) Mixed event w BG1 BG2 Reconstructed invariant mass Peripheral (cent 60~92 %) 3.5<pT<4.5[GeV/c] BG2 Black: FG Magenta:BG1+BG2+BG3 count BG3 BG1 after subtraction of BG1+BG2+BG3 w [GeV/c^2] Gaussian (Mean and With are Fixed by Embedding simulation)

  11. Results & Discussion Whatdo we see? • Spectra (p+p & d+Au)

  12. Results & Discussion Whatdo we see? Getting down in higher centrality • Spectra (Au+Au) w p0g , w e+e-@ Au+Au Suggesting Hadron suppression

  13. Results & Discussion Whatdo we see? Interesting systematic measurement of hadron suppression

  14. Results & Discussion Whatdo we see? Interesting systematic measurement of hadron suppression

  15. 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

  16. Back up

  17. Chiral Symmetry Restoration Phys.Rev.Lett.55(1985)158. Nucl.Phys.A443(1993)59c. Chiral symmetry is spontaneously broken <qq>~250 MeV ｰ 3 Chiral symmetry is restored <qq> → 0 ｰ (Heavy Ion Collider used for this study)

  18. Prediction of theory T.Hatsuda and S.H.Lee P.R.C.46(1992)R34 → R.Rapp,H.Hees and T.Strong hep-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!

  19. Phi results wφ e+e- , φ K+K- @ Au+Au φ K+K-@ Au+Au

  20. d+Au results (omega) w p0g , w p0p+p- @ d+Au

  21. STAR results

  22. RAA with direct photon

  23. Cut Optimization If there’s no cut, S/B< 1/1000…. →Have to improve it by the selection ･Pi0 Momentum Cuts ･Photon Energy Cuts ･Pi0 Mass Width Great influence on the peak significance Pi0 Momentum Cuts Photon Energy Cut Pi0 Mass Width S/√B Cut#4 Cut#3 Cut#2 Cut#1 Default ex. 4.5<ωpT<5.5 (GeV/c)

  24. Estimation of omega cross-section

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