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単電子および電子対測定の物理、現状、展望

単電子および電子対測定の物理、現状、展望. 蜂谷　崇 広島大学 /PHENIX collaboration. Physics Motivation. Search for the new State of Matter (quark-gluon-plasma) and study its properties. Leptonic Observables Why do we want to measure leptonic observable?

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単電子および電子対測定の物理、現状、展望

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  1. 単電子および電子対測定の物理、現状、展望 蜂谷　崇 広島大学/PHENIX collaboration

  2. Physics Motivation • Search for the new State of Matter • (quark-gluon-plasma) and study its properties. • Leptonic Observables • Why do we want to measure leptonic observable? • Heavy flavor (Charm): Single Electrons (c  D  e + X) • Quarkonia: J/ e+e-, • Light vector mesons:   K+K-, e+e- , , also • Dielectron Continuum: • Low and Intermediate Mass Region • Photons: Direct (prompt and thermal) photons • via its conversions Pair wise observable Workshop at RCNP

  3. J/ measurement Workshop at RCNP

  4. Motivation of J/ measurement • Debye color screening will lead to a suppression of • charmonium production in heavy ion collisions. • one of the earliest probe of the QGP • Predictions of enhanced J/ • production at RHIC energy • from recombination • in final state interaction. • NA50 measured J/ • at SPS energy. They found • an anormalous suppression. • Systematic study is needed to • disentangle the compete effect. Workshop at RCNP

  5. PHENIX Experiment • Two central spectrometers • , e and hadrons • || < 0.35,  = /2  2 • Two fwd spectrometers •  • 1.2 < || < 2.4 EMCAL RICH BBC DC&PC Workshop at RCNP

  6. PC3 PC2 RICH PC1 DC Mirror All charged tracks e+ X e± real. Ring in RICH EM Calorimeter Net e± Cherenkov light in RICH BG Electron Measurement • Electrons are measured by • DC→PC1→RICH→EMCal • Electron Identification : • Cherenkov light in RICH • Number of Hit PMT • Ring shape • Energy – Momentum matching Workshop at RCNP

  7. J/ in p+p at s = 200 GeV baseline measurement p+pJ/Y+X at s = 200 GeV (Run 3) PHENIX preliminary • good agreement with: • lower s data and phenomenological extrapolation • Run 2 and Run 3 data p+pJ/Y+X at s = 200 GeV PHENIX PRL 92, 051802 (2004) Workshop at RCNP

  8. J/  in d+Au Nuclear Effects • Modification of the parton distribution functions: • Gluon shadowing -> reduction of production at low x. • 3 rapidity ranges in PHENIX probe different • momentum fraction of Au partons • South (y < -1.2) : large X2 (in gold) • Central (y ~ 0) : intermediate • North (y > 1.2) : small X2 (in gold) Predicted Gluon Shadowing in d+Au From Eskola, Kolhinen, Vogt Nucl. Phys. A696 (2001) 729-746. Workshop at RCNP

  9. J/y in pp and dAu collisions at RHIC J/y production in d+Au is compared in p+p d  Au Workshop at RCNP

  10. Low x2 (shadowing) S.B. Klein and R. Vogt, nucl-th/0305046 J/y d+Au/p+p vs rapidity • indication for (weak) shadowing and absorption • more statistics desirable to disentangle nuclear effects (and distinguish models) Rapidity d  Au Workshop at RCNP

  11. 40-90 % central Ncoll = 45 20-40 % central Ncoll = 296 normal nuclear absorption 0-20 % central Ncoll = 779 SPS NA50 normalized to p+p point Au+AuJ/Ye+e- at sNN = 200 GeV PHENIX PRC 69, 014901 (2004) J/in Au + Au at sNN=200 GeV (run2) PRC 69, 014901 (2004) • Need more statistics • inconsistent with large enhancement scenarios Workshop at RCNP

  12. Au + Au Coming attraction of J/ analysis • Au + Au analysis • Run2 • 25 M (MB) + 25M (LVL2) events • Run4 • 1.6 B eventswith healthy detector • 20-30 times larger statistics • Bdn/dy/Nbinary • Accurate study of the centrality dependence • We see the clear J/ signal. Workshop at RCNP

  13. Current Status of J/ • J/ has been measured in p+p, d+Au, Au+Au • Nuclear effects are studied in d+Au • Weak shadowing • Smaller absorption than expected ( > 0.92) • Statistics is limited---- Need more data. • We have 1.6B MB data in Run 4 (Au+Au) • Quantitative study of J/ production in Au+Au Workshop at RCNP

  14. Light vector meson measurement Workshop at RCNP

  15. Motivation of light vector meson (LVM) measurement • Looking for (partial) Chiral symmetry restoration • LVM has Short lifetime ~ few fm/c • Decay inside medium. • Mass modification of vector mesons is expected. • Au + Au and d +Au collisions • Distinguish between hot and cold partonic matter • Probing nuclear effects T.Hatsuda and S.Lee (Phys.Rev.C46-1 1992) Quark mass in vacuum mu ~ md ~ 5 MeV/c2 ms ~ 100 MeV/c2 Effective quark mass in hadron mu ~ md ~ 300 MeV/c2 ms ~ 500 MeV/c2 Workshop at RCNP

  16. Fit is to relativistic Breit-Wigner convoluted with a Gaussian (detecter) N~120 in e+e– mode and N = 207  16 in K+K– mode Both measurements are consistent with PDG   e+e-   K+K- Combinatorial Background Yield Yield Minv (GeV/c2)  measurement ind+Au at sNN = 200 GeV Workshop at RCNP

  17. PHENIX Preliminary dAuee dAuKK 1/2mT dN/dmTdy(GeV/c2)-2 PHENIX Preliminary dN/dy MT(GeV/c2) K+K– e+e– Minimum-bias mT distribution of f • K+K– channel dN/dy = 0.0468 +/- 0.0092(stat) (+0.0095,-0.0092) (syst.) • e+e– channel dN/dy=.056.015(stat) 50%(syst) yields in d-Au collisions in K+K- and e+e– channels are consistent. Workshop at RCNP

  18.  measurement inAu+Au at sNN = 200 GeV Yield • Clear signal in KK channel • No clear signal in ee channel, due to small statistics • Mass centroid and width is consistent with PDG • No-dependence with centrality nucl-ex/0410012 Workshop at RCNP

  19. e+e– invariant mass r+w work in progress Yield f r,w,f in near future • Full statistics available inRUN3 d+Au. • Background subtracted mass spectra • Amount of data is twice • Large statistics in Run 4 Au+Au dataset • r,w,fsignal inMee spectrum can be seen Workshop at RCNP

  20. Current Status of LVM •  is measured in both K+K– and e+e– channel in d+Au •  yields in d-Au collisions in K+K– and e+e– channels are consistent. • Mass centroid and width is consistent with PDG •  is measured in K+K– channel in Au+Au • Not so clear signal in e+e– channel • Mass centroid and width is consistent with PDG • Not depend on centrality • We have more statistics in both d+Au and Au+Au • In d+Au, data can be twice • In Au+Au, 1.6B min. bias data in run 4 (20M in run2) Workshop at RCNP

  21. Heavy Flavor Measurement using Single Electrons Workshop at RCNP

  22. Motivation of Heavy flavor Measurement • Charm is produced through mainly gluon-gluon • fusion in heavy ion collisions • Sensitive to gluon density in initial stage of • the collisions • Charm is propagated through hot and dense • medium created in the collisions • Energy loss of charms via gluon radiation • (dead cone effect?, else…) • Charm can be produced thermally at very high • temperature • Sensitive to state of the matter • Charm measurements bring us an important baseline of J/ Workshop at RCNP

  23. Heavy flavor in p+p, d+Au and Au+Au • p + p measurement • Test pQCD calculation • Baseline measurement for d+Au and Au+Au • d + Au measurement • Normal nuclear effect • Cronin effect • Gluon shadowing • Au + Au measurement • Total yield • Expected to scale with binary collision • Spectral shape at higher pT • Study charm energy loss in dense medium • Charm Flow • V2 measurement  Sakai-san’s Talk Workshop at RCNP

  24. p+ Charm Measurement Indirect method: Measure leptons from semi-leptonic decays of charm. This method is used by PHENIX at RHIC Direct method: Reconstruction of D-meson (e.g. D0Kp). • Very challenging without measurement of displaced vertex. Workshop at RCNP

  25. Source of Electrons All electrons measured in experiment are EM force origin and Weak force origin Non-PHOTONIC signal • Charm decays • Bottom decays Background • Photon conversions : • p0,h,h’,w,fDalitz decays (p0eeg, heeg, etc) • Conversion of direct photons • Di-electron decays ofr,w,f • Thermal di-leptons • Kaon decays (weak decay) Most of the backgrounds are PHOTONIC PHOTONIC All back grounds should be subtracted to extract the signal Workshop at RCNP

  26. Photon Converter Extraction of Non-photonic Electrons (Heavy flavor Electrons) • Converter method • Comparison of electron yield • with and without the converter • allows to separate the photonic • and the non-photonic electrons. • Cocktail method • Light hadron cocktail. • Major source (0) is measured by the PHENIX spectra. • Other mesons are estimated by mt scaling assumption • and asymptotic ratios from lower energy data. • Photon conversion from material in PHENIX acceptance. Workshop at RCNP

  27. Result (from PHENIX)p+p (reference for all other system)d+Au (nuclear effect)Au+Au (Suppression? Enhancement?) Workshop at RCNP

  28. Non-Photonic Electrons in p+p at s = 200 GeV PHENIX PRELIMINARY • 200 GeV pp non-photonic electron spectrum from cocktail subtraction method • PYTHIA tuned to low energy data • Data is harder than PYTHIA charm + bottom above pt=1.5 GeV/c Workshop at RCNP

  29. Non-Photonic Electrons in d+Au at sNN=200GeV PHENIX PRELIMINARY • 200 GeV dAu non-photonic single electron spectrum from converter method • Data divided by TAB Spectacular agreement within stated errors • No indication for strong cold-nuclear matter effects 1/TABEdN/dp3 [mb GeV-2] 1/TAB Workshop at RCNP

  30. Centrality Dependence in d+Au at sNN = 200 GeV PHENIX PRELIMINARY PHENIX PRELIMINARY 1/TABEdN/dp3 [mb GeV-2] 1/TABEdN/dp3 [mb GeV-2] 1/TAB PHENIX PRELIMINARY PHENIX PRELIMINARY 1/TABEdN/dp3 [mb GeV-2] 1/TABEdN/dp3 [mb GeV-2] 1/TAB Workshop at RCNP

  31. Status in p+p and d + Au • In p + p, the spectra are described by PYTHA at low pT. • Spectra are “harder” than PYTHIA at pT > 1.5 GeV/c: • Non-photonic electrons in d+Au agree well with pp fit and binary scaling. • for whole pT range and all centrality bins. • No indication for strong nuclear effect • What happened in Au + Au ? Workshop at RCNP

  32. Non-photonic Electron in Au+Au at sNN = 200 GeV • 200 GeV Au+Au non-photonic single electron spectrum from converter method • Data is divided by TAA and overlaid with PHENIX pp fit • At low pt the pp fit is in good agreement 1/TABEdN/dp3 [mb GeV-2] 1/TAA Workshop at RCNP

  33. Centrality Dependence in Au+Au at sNN = 200 GeV 1/TABEdN/dp3 [mb GeV-2] 1/TABEdN/dp3 [mb GeV-2] 1/TAA 1/TAA 1/TABEdN/dp3 [mb GeV-2] 1/TABEdN/dp3 [mb GeV-2] 1/TABEdN/dp3 [mb GeV-2] 1/TABEdN/dp3 [mb GeV-2] 1/TAA 1/TAA 1/TAA • Consistent with binary scaling • Small statistics for high pT Workshop at RCNP

  34. nucl-ex/0409028 Ncollision Scaling in Au+Au • Quantitative study of binary scaling. • Fit dN/dy (0.8<pT<4.0) = A (Ncoll) =1  complete binary scaling •  = 0.938  0.0798 (+0.0201–0.0148) without p+p = 0.958  0.0351 with p+p • Non-photonic (charm) electron production is consistent with number of binary collisions scaling. Ncoll Workshop at RCNP

  35. Charm Cross Section • PHENIX measures cc = 622  57  160 b in Au+Au at 200GeV (MB) • NLO calculation shows cc = 300~450 b • Total cross section is consistent with pQCD calculation Workshop at RCNP

  36. Coming attraction Converter vs Cocktail p+p and d+Au at sNN=200GeV Au+Au at sNN=62.4GeV PHENIX Preliminary Work in progress • Converter vs Cocktail method • The pT distributions are in good agreement. • The converter is good for lower pT, the cocktail is good for higher pT • Energy loss effect can be studied by cocktail method. • Systematic study is now proceeding. • p+p at sNN 200GeV in Run2 • p+p and d+Au at sNN 200GeV in Run3 (much more statistics) • Au+Au at sNN =62.4GeV and 200GeV (much more statistics) Workshop at RCNP

  37. Status in Au + Au • Total non-photonic electron yield in Au+Au agree well with binary scaling. • Total cross sectioncc = 622  57  160 b •  = 0.938  0.0798 (+0.0201–0.0148) without p+p • Small statistics for high pT measurement • Systematic study is now in progross. • Refine Au+Au data by cocktail method. • P + p, d + Au and Au + Au measurement with higher statistics • PHENIX detector upgrade • Silicon vertex to reconstruct displaced vertices • D → K p, B → J/y K • Hadron blind detector • High electron identification capability Workshop at RCNP

  38. Summary • PHENIX measured leptonic observables • j/ in p+p, ｄ＋Au, Au+Au at sNN = 200GeV. • Light vector mesons in d+Au and Au+Au. + Both   K+K–,   e+e– are measured in d+Au. • Non-photonic electrons in p+p, d+Au, Au+Au • Total charm production in Au+Au is consistent with binary scaliing. • no indication for strong enhancement / suppression of charm cross section in nuclear collision. • Systematic study with wide range of system and kinematic now begins • Much more statistics in Run 4 • Detector upgrade will provide new opportunity Workshop at RCNP

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