1. 2008 Oct. ATHIC @ Tsukuba 1 Misaki Ouchida Hiroshima University For the PHENIX Collaboration ω ω ω e＋e＋ eーeー γ γ π+π+ π0π0 γ πーπー π0π0 γ γ Low mass vector meson measurements at RHIC Systematic Measurement of omega mesons in PHENIX ー ー

2. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 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. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 3 Introduction Why Low Mass Vector mesons? Physics… Low pT High pT Signal for Chiral Symmtery Restoration p+p d+Au A+AA+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 Reconstructed Reconstructed Efficiency Efficiency   e + e - (BR:7x10 -3 %)     (BR:9%) ωpT Signal for Jet Quenching

4. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 4 Suppression as a Probe of QGP PRL 91. 072301 (2003) Nuclear Modification Function QGP In the absence of nuclear effects: R AA =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?

5. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 5 e+e+ e-e- MomentumElectron ID π-π- φ→e + e - ω→e + e - π+π+ ω γ γ π0π0 γγ γ γ π0π0 ω→π 0 π + π - ω→π 0 γ Energy Momentum Hadron ID PHENIX spectrometer BBC & ZDC : Event trigger, Collision vertex, Centrality Acceptance ⇒ pseud-rapidity range : |η| < 0.35 azimuthal angle : 2x90 degree DC & PC : tracking, momentum RICH & EMC : electron ID TOF, EMC : hadron ID MuID : muon ID ⇒ PHENIX consists of multi-purpose detector to measure rare probe from collisons. Experiment Which decay mode do we measure ?

6. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 6 p+p, d+Au collisions Analysis Highlight How do we approach? p+p d+Au      e+e-   +  -   p+p Both leptonic and hadronic decay channel are measured

7. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 7 Quest for Low Mass Vector Mesons in huge huge Background Analysis Highlight How do we approach? Challenge to A+A Collisions

8. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 8 Analysis Highlight How do we approach? Improving S/N pT(ω) [GeV/c] S/√B (significance) No Cuts Best Cuts Further Cut Optimization e.g.     @ 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

9. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 9 Analysis Highlight How do we approach? AN 612 Subtracting Backgrounds ( 2 body:  e+e-  K + K - )  BG conbinatorial backgrounds Extract by Event Mixing  →ee BGSignal

10. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 10 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 of BG1+BG2+BG3 count Reconstructed invariant mass Mixed event Analysis Highlight How do we approach? Subtracting Backgrounds ( 3 body:     (    2  ) 

11. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 11 Spectra (p+p & d+Au) Results & Discussion What do we see?

12. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 12 Spectra (Au+Au)    ,  e+e- @ Au+Au Results & Discussion What do we see? Suggesting Hadron suppression Getting down in higher centrality in higher centrality

13. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 13 Results & Discussion What do we see? Interesting systematic measurement of hadron suppression

14. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 14 Results & Discussion What do we see? Interesting systematic measurement of hadron suppression

15. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 15 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 decay channels in p+p and d+Au –A+A results have an ability to discuss hadron suppression providing intriguing systematic results. Physics… Low pT High pT Signal for Chiral Symmtery Restoration Signal for Hadron Suppression yet to be discussed… provide intriguing result Systematic measurement of omega in PHENIX will be published in near furture

16. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 16 Back up

17. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 17 Nuclear Modification Function: R AA     @ Au+Au Results & Discussion What do we see?  K + K - @ Au+Au Suggesting Hadron suppression same as other mesons Suggesting Hadron suppression same as other mesons

18. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 18 Spectra (A+A)    ,  e+e- @ Au+Au  e+e-  K + K - @ Au+Au Results & Discussion What do we see? Suggesting Hadron suppression same as other mesons PHENIX Preliminary PHENIX Preliminary & Work In Progress

19. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 19 Analysis Highlight How do we approach? Cu+Cu     RHIC Chose the data set that only take high pT  High statistic EMCal Using detector thresholds

20. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 20 0-20% 20-60% 60-92% M.B. Omega Spectra (together)

21. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 21 PHENIX

22. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 22 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 corrected Energy 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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28. Misaki Ouchida2008 Oct. ATHIC @ Tsukuba 28 d+Au results