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PHENIX における 最新のレプトン対測定結果

PHENIX における 最新のレプトン対測定結果. 小沢恭一郎 東大・理. Open Questions. Formation of hot and dense matter is established. Still, we have many important questions to answer. Is the matter deconfined ? J/ y suppression How does Heavy-flavor act? Heavy flavor measurements Is Chiral symmetry restored?

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PHENIX における 最新のレプトン対測定結果

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  1. PHENIXにおける最新のレプトン対測定結果 小沢恭一郎 東大・理

  2. Open Questions Formation of hot and dense matter is established. Still, we have many important questions to answer. • Is the matter deconfined? • J/y suppression • How does Heavy-flavor act? • Heavy flavor measurements • Is Chiral symmetry restored? • Vector meson • Radiation? Mass shift? • Di-lepton continuum Heavy Ion Cafe @ Hongo

  3. @SPS

  4. CERES Heavy Ion Cafe @ Hongo

  5. CERES 2 Heavy Ion Cafe @ Hongo

  6. NA60 • and  : fix yields such as to get, after subtraction, a smoothunderlying continuum •  : ()set upper limit, defined by “saturating” the measured yield in the mass region close to 0.2 GeV/c2 (lower limit for excess). () use yield measured for pT > 1.4 GeV/c Heavy Ion Cafe @ Hongo

  7. What’s this? [van Hees+RR ‘06] • absolute norm., meltingr • M>0.9GeV: “4p”→mm; w and f ?! • baryon effects essential Heavy Ion Cafe @ Hongo

  8. Model 2 Contributions included in our calculation: QGP quasi-particle picture, (Schneider et al. (2002)) In-medium Rho spectral function (Eletsky et. al. (2001)) In-medium Omega spectral function (Martell & Ellis (2004)) In-medium Phi not (yet) included Renk, Ruppert (2006) (Results were obtained by folding with the schematic acceptance matrix,not the full MC acceptance simulation.) Heavy Ion Cafe @ Hongo

  9. φ・ω@RHIC

  10. Mass shift and/or modification of vector mesons are expected Lepton decays become good probes Not interacting “strongly.” However, we only see integrated information from all stages of collisions. QGP, Mixed, Hadron gas Comparisons between lepton decays and hadron decays in several collision systems are important Chiral Symmetry in Hadronic matter R. Rapp (Nucl. Phys A661(1999) 238c After Freeze Out Hadron gas QGP • Integrated information Heavy Ion Cafe @ Hongo

  11. Observables in vector meson measurements • Line shape • Direct measurements • Yield • Q value of f→ KK is small • Should be sensitive to mass changes in either f or K • pT slope • Difference between hadron decays and lepton decays • It could show the difference of collision stage. Lissauer and Shuryak, Phys. Lett. B253, 15 (1991). T.Hatsuda and S.Lee (Phys.Rev.C46-R34-38, 1992) Heavy Ion Cafe @ Hongo

  12. Measurement J/y ω φ ●Au＋Au ●p+p Dalitz Conversion g After BG subtraction Raw spectrum (Combinatorial BG included) Invariant mass spectrum of e+e- in PHENIX 0 1 2 3 [GeV/c2] Clear f, w, and J/y peaks with very good mass resolution!! Heavy Ion Cafe @ Hongo

  13. f: hadron and lepton decays Main issue: K+K- and e+e- seem not consistent Many efforts are on-going to understand the difference btw K and e. We have to prove that the difference is not made artificially. Analysis in d+Au and p+p data is important as baseline. Heavy Ion Cafe @ Hongo

  14. S = 786 ± 34, S/B = 1/0.47 Baseline - dAu d – Au collisions at √sNN = 200 GeV f e+e- f K+K- Combinatorial Background Counts per 10 MeV/c2 • N~120 PHENIX Preliminary PHENIX Preliminary e+e- invariant mass (GeV/c2) To settle cold nuclear matter effect, Both f e+e- andf K+K- are measured in d-Au collisions and results are compared. K+K- invariant mass (GeV/c2) Heavy Ion Cafe @ Hongo

  15. dN/dy in dAu • dN/dy is compared between ee and KK. dN/dy KK channel dN/dy = 0.0468 +/- 0.0092(stat) (+0.0095,-0.0092) (syst.) ee channel dN/dy=.056.015(stat) 50%(syst) dN/dy KK No significant difference between ee and KK within statistical and systematic errors. ee PHENIX preliminary Heavy Ion Cafe @ Hongo

  16. p+p omega phi ds/dy Extracted by integration OMEGA: 3.50037 +/- 0.175942 (stat) +/- 0.875 (sys) 4.37554 (upper sys) 2.62521 (lower sys) PHI: 0.369182 +/- 0.0195987 (stat) +/- 0.0894 (sys) 0.458564 (upper sys) 0.2798 (lower sys) 来島 Heavy Ion Cafe @ Hongo

  17. Spectra of w meson are measured in several collision systems. w spectra • p+p • d+Au • Au+Au • Results are mainly obtained using hadron decays. • Analysis for electron decay mode is underway. Heavy Ion Cafe @ Hongo

  18. New approaches for f and w • f in p+p • It works very well especially in high pT region • Combinatorial BG is decreased • Improved BG estimation • w in Au+Au wp0g No PID method for f  K+K- Heavy Ion Cafe @ Hongo

  19. Next steps • Analysis for run4 should be completed soon • Improved statistics and background in run7 • Improved understanding for dAu • Figure out how to analyze r mesons (short lived) • r→ p+p- at STAR (Phys. Rev. Lett. 92, 092301) • Try many measurements to figure out chiral symmetry restoration • Line shape? • Yield? Slope? • Ratio between hadron and electron or f and w • Ratio to p0 Heavy Ion Cafe @ Hongo

  20. electron positron continuum

  21. Broadening of r meson makes continuum on the invariant mass of electron-positron pair In addition, thermal radiation by the system via quark anti-quark annihilation also makes continuum and it carries direct information from the matter. Matter is formed Deconfinement Thermalized Experimentally, combinatorial background is very large and must be subtracted properly. Also, useful for charm measurements electron-positron continuum • A prediction • R. Rapp, nucl-ex 0204003 Heavy Ion Cafe @ Hongo

  22. submitted to Phys. Rev. Lett arXiv:0706.3034 Results Clear enhancement is observed in the mass region below w. Heavy Ion Cafe @ Hongo

  23. p+p MULTIPLIED by Ncoll pp – AuAu comparison p+p NORMALIZED TO mee<100 MeV Heavy Ion Cafe @ Hongo

  24. Centrality Dependence LOW MASS • p0 production scales with Npart • If in-medium enhancement from pp or qq annihilation yield should increase faster than proportional to Npart INTERMEDIATE MASS • p0 production scales with Npart • charm follows binary scaling yield should increase proportionalto Ncoll Heavy Ion Cafe @ Hongo

  25. Further analysis Cu+Cu • Comparison with CuCu • Comparison with SPS • Finalizing pp • Reasonable normalization of pp • Npart for low mass? • Ncoll for charm? • Improved statistics in run7 • pT dependence • reaction plane dependence • Use HBD to suppress background Heavy Ion Cafe @ Hongo

  26.  e+ e - po   e+ e - signal electron partner positron needed for rejection Hadron Blind Detector • Background is made by combination of non-correlated e+e- pair, • e+e- from Dalitz and g rejected by new detector “combinatorial pairs” all signal Dalitz rejector Hadron Blind Detector Heavy Ion Cafe @ Hongo

  27. photon Heavy Ion Cafe @ Hongo

  28. Thermal photon Turbide, Rapp, Gale, Phys. Rev. C 69 (014903), 2004 • Direct photon • Directly emitted from the medium • Not from hadron • Hard photon • Initial pQCD • Thermal photon • Hadron gas • QGP After subtraction of large background from hadron decays, Window for thermal photons from QGP in this calculation: pT = 1 - 3 GeV/c pQCD calculation should be confirmed in High pT region Heavy Ion Cafe @ Hongo

  29. g*direct g g g*incl. p0 p0 e+ g* g e- Compton e+ g* g q e- q g g q q can be measured. Idea - g* e+e- Any source of real g emits virtual g with very low mass Dalitz decay Use lepton pairs to measure virtual g and extrapolate to real g PHENIX can measure low mass e+e- pairs hadron decays and direct photon *In the analysis, Mee distribution for Dalitz and direct photon is calculated theoretically. Therefore, the ratio of Nee in two different mass region is converted to the ratio between direct and inclusive photons. The systematic error is reduced. Heavy Ion Cafe @ Hongo

  30. ~25 % systematic error : ~20 % from measured h/p0 ratio ~10 % from g inclusive ~5 % acceptance g*direct / g*inclusive Significant 10% excess of very-low-mass virtual direct photons Heavy Ion Cafe @ Hongo

  31. g*direct g*incl. gdirect gincl. g*direct / g*inclusive Significant 10% excess of very-low-mass virtual direct photons Results agrees well with Conventional result One can extract the direct photon yield from the inclusive photon yield. = Heavy Ion Cafe @ Hongo

  32. Direct photon yield Direct photon yield is calculated from the inclusive photon yield. Heavy Ion Cafe @ Hongo

  33. Direct photon yield Direct photon yield is calculated from the inclusive photon yield. Compare to NLO pQCD L.E.Gordon and W. Vogelsang Phys. Rev. D48, 3136 (1993) Excess above the calculation It might include contribution from thermal photons Reference measurement needed pp and dAu Using same analysis method Heavy Ion Cafe @ Hongo

  34. Compare to NLO pQCD • L.E.Gordon and W. Vogelsang • Phys. Rev. D48, 3136 (1993) • excess above pQCD Thermal photon? Compare to thermal model • D. d’Enterria, D. Perresounko • nucl-th/0503054 2+1 hydro T0ave=360 MeV(T0max=570 MeV) t0=0.15 fm/c • data above thermal at high pT Heavy Ion Cafe @ Hongo

  35. ｐ＋ｐ 山口 Heavy Ion Cafe @ Hongo

  36. Recalculation of Rg* in p+p PHENIX Preliminary Stat.errors on simulation are included in sys.errors on Rg*. It should be reduced. Heavy Ion Cafe @ Hongo

  37. Comparison of Rg* with Run4-central result PHENIX Preliminary Heavy Ion Cafe @ Hongo

  38. Summary So many interesting analysis topics are on-going at PHENIX Such as, Heavy flavor measurements, J/y, f, and lepton pair continuum Measurement for chiral symmetry is underway. First result will publish soon. Enhancement is observed in e+e- continuum! Interesting results in Direct photon measurements. We are still in an exciting time! Heavy Ion Cafe @ Hongo

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