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Physics motivation Status Experiment f →K + K － results & w/r →e ＋ e － results

Measurements of in-medium decay of vector mesons Hideto En’yo RIKEN / Kyoto University for The KEK-PS E325 Collaboration. Physics motivation Status Experiment f →K + K － results & w/r →e ＋ e － results Discussion & Summary. Tantalizing hints for new state of matter.

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Physics motivation Status Experiment f →K + K － results & w/r →e ＋ e － results

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  1. Measurements of in-medium decay of vector mesonsHideto En’yo RIKEN / Kyoto UniversityforThe KEK-PS E325 Collaboration Physics motivation Status Experiment f →K+K－ results & w/r →e＋e－ results Discussion & Summary Hideto En'yo, RIKEN

  2. Tantalizing hints for new state of matter CERN Press Release Feb. 2000 Hideto En'yo, RIKEN

  3. What Theorists Say ? • <qq> quark condensate : order parameter • to indicate how much the symmetry broken • but not an observable • →Mass of Vector Meson, r w f • Mv = 2 x Mqeff + small interaction term Hideto En'yo, RIKEN

  4. Bound Nucleons, Mesons • Imagine that a neutron ( or proton ) in Oxygen nuclei made GUT decay in Kamiokande. (assume that you have a perfect detector ) n→ π+ + e- Mn2 → ( Eπ+ Ee)2 -(Pπ+ Pe)2 Mn= 939.6 MeV , Mn= 938.3MeV ????? • More precisely 16O → π+ + e- + 15O* (Mn +M15O )2 → (E15O +Eπ+ Ee )2 - (P15o+ Pπ+ Pe )2 E2=M2+P2 You measure 16O levels Hideto En'yo, RIKEN

  5. Moving Mesons in Media • In-media meson modification • Observed Mass is not Lorentz Invariant • shift of resonance position • resonance broadening/narrowing →DISPERSION E2=M2+P2 Outside be small Inside Hideto En'yo, RIKEN

  6. Experiments CLUES Experiment Measurements Interests CERES/HELIOS-3r modification Temp. dep. ρis modified in Hot Matter KEK-TANASHI ESr modification Density dep. ρis modified in He GSI p modification Density dep. πis modified in He Present & future experiments . RHIC(running)/LHC(2006) KEK-PS: p+A→f+X(f→K+K-/e+e-) (Running) SPring-8: g + →f+A*(f→ K+K-) (Ready to run ) GSI: d +A→3He+A* (hw bound states) (Ready to run ) GSI-HADES: p +A→ w+A* (w→e+e-) (Preparation, 2001?) Hideto En'yo, RIKEN

  7. KEK-PS E325 to measure ρωφ decaysin nuclear matter f(G=4.4MeV) DQ=38MeV φ →K+K- /φ →e+e- KK Threshold in Free Space f modification ? K modification ? Shape modification can bemeasured in ω/ρ/φ →e+e- Hideto En'yo, RIKEN

  8. Some Tips of E325 • 109/sec primary protons on thin (0.1%) nuclear target to suppress g conversions. • Focus on slowly moving f,w,r 's, p =~1GeV/c(lab).About 10% of f's will decay inside a nucleus if nothing happens. • Expected mass shift is 20~40 MeV for φ　～140MeV for ρ、ω • ( Hatsuda-Lee). • Secondary peak may enhance when low b f's are selected. • The ratio (f→K+K-)/(f→e+e-) is sensitive to modification of phi and/or K • natural width of f, w is narrow (4.4, 8.4MeV), but some broadening can happen.. Estimations are: • Gf = sfNbfr0Gf <20MeV • s{fN} < $10mb, total cross section (from g+A→f )bf=0.7,r0 =0.16/fm3 • f →K+*K-*(K-N→SX) • Klingle and Weise Gf ~44MeV (at rest) Hideto En'yo, RIKEN

  9. Brief Mile Stones and Status Analysis • 1994 March. KEK-PS PAC conditionallyapproved • 1995 March. KEK-PS PAC approved • 1996 July. Construction started • 1996 November. Engineering Run (40.5shift of beam test) • 1997 June, First Physics Run with K+K-. 17days 50 shifts • Data accumulation mainly with K+K- channel trigger • Beam Intensity 1~2 x108$ protons/spill on 0.6% interaction targets (106 interaction/spill) • 1998 March. Completion of Spectrometer, • 1998 April –May. Production Running of 29 days 74shifts. • Parallel Trigger. K+K-/ e+e- • Beam Intensity 1~2 x 109 protons/spill on 0.1% interaction target (106$ interaction/spill) • 1999 June 57 shifts Data Taking performed • Parallel Trigger. K+K-/ e+e- • Beam Intensity 1~2 x 109 protons/spill on 0.2% interaction target (106$ interaction/spill) • 2000 Jun, 35shifts • 2000 Dec. Data Taking to start now. • 104 shifts to go in 21st Century ! KK ee Hideto En'yo, RIKEN

  10. E325 collaboration ICEPP, U-Tokyo S.Mihara M.Ishino • Kyoto University H.Funahashi,, M.Kitaguchi, M.Miyabe, T.Murakami, R.Muto, M.Naruki, F.Sakuma, H.D. Sato, S.Yamada • CNS, University of Tokyo • H.Hamagaki, K.Ozawa • Tohoku University • H. Kanda • KEK • J.Chiba, M.Ieiri, O.Sasaki, M.Sekimoto, K.Tanaka • Osaka University • M.Nomachi • RIKEN • S.Yokkaichi,T.Tabaru, H. Enyo Companies T.Miyashita Y.Yoshimura K.Hamada Hideto En'yo, RIKEN

  11. E325 SETUP Hideto En'yo, RIKEN

  12. Hideto En'yo, RIKEN

  13. Around the targets • 3 target plate inline • C/CH2/Cu • 109/s protons， • 106/s interactios • Vertex chamber • 1.75mm drift length Hideto En'yo, RIKEN

  14. Spectrometer Performance (Invariant Mass Spectrum) L→pp- K0→p-p+ MK= 494.8MeV/c2 (PDG497.7MeV/c2) dMk = 6.1MeV/c2 (Sim 6.3MeV ) ML= 1115.4-5MeV/c2 (PDG1115.7MeV/c2) dML = 1.8-2.4MeV/c2 (Sim 1.9MeV) φ→KK 2．4MeVφ→ee9MeV Hideto En'yo, RIKEN

  15. ‘98 data (Electron Channel) Nucl-ex-0011013 to appear in PRL • ω→e+e－　　SignificantDifferencebetween C and Cu • The first observation of in-medium decay of vector mesons. Hideto En'yo, RIKEN

  16. ‘99 data (KK mode) to be published Hideto En'yo, RIKEN

  17. βγ Pt JAM (Y.Nara, RBRC)Intra Nuclear Cascade Code • Resonance Production ( Low Energy) • String Excitation (Mid Energy) • Parton-parton (High Energy) • K+K- Sources • φ • a0/f0 • Non resonant (not large) • PID back ground • C,CH2 data (χ2 = 34.5/37) • a0/f0 to φ37．7±10 % • Gd,Cu data (χ2 = 38.8/37) • a0/f0 to φ27.2±10．1％ JAM All come from string decays Ｙ－Pt Y Experiment Kinematical Distributions are well Described by JAM Hideto En'yo, RIKEN

  18. Target Mass Dependence ofsf→K+K- (’97+’99 Data) a=1.010.09 EXP a=1.080.01 JAM a is surprisingly large but explained by JAM. For Carbon Ωσ= 0．190.030.09 μｂEXP Ωσ= 0．310.03 μｂ　　　　JAM σ= 15.5 Aαμｂ　JAM Hideto En'yo, RIKEN

  19. Target Mass Dependence ofs(φ,ω)→e+e- (’99 Data) a= 0.63± 0.07 for ωpeak a=1.03± 0.15 for φpeak C/CH2 ω→e+e－ φ→e+e－ Hideto En'yo, RIKEN

  20. What we have learned ? Toy Model Calc. • Meson modification is observed in nucleus firstly in electron pair channel. • Does it means QCD chiral symmetry restoration ? • NOTYET ( life is more complicated) • mass shift as predicted by Hatsuda • in-media broadening of 3 × free • space ( D. Cabera et al.) • production of ρ・ω at the surface • of a nucleus （A 2/3） Hideto En'yo, RIKEN

  21. What is missing then ? • Theoretically • How large the in-media broadening ? • SHAPE • DECAYRATE Many theoretical works, not conversing • Other trivial reasons ? • Collisional broadening • Phase space (not important in E325) • Experimentally • Statistics, Statistics, Statistics, to give • Accurate shape • Dispersion • φ→e+e－ By Akaishi, Yamazaki Hideto En'yo, RIKEN

  22. Summary and Outlook • The ’97+’99 f→K+K- data have been analyzed. The results shows • No significant mass shape deformation (a0/f0 are problematic) • Strong A dependence (a =1.01 +- 0.09 ) in the production • Reasonable agreement with the cascade model JAM. • The ‘98 ω→e+e- spectrum shows a surprising indication of in-medium decay of ρ/ω mesons • The first observation of mesons decayed in nuclear matter. • The physics underneath is not apparent yet, but very promising to go further. • The ‘99 e+e- data are still preliminary, with a clear peak of φ →e+e- • Adependence of ω andφproductions are ~2/3 and ~3/3 , respectively • Statistics will be ＞5times at the end of assigned beam time, φ→e+e-and dispersion data will be available Will hopefully be the first measurements to address the chiral property of dense nuclear matter. Hideto En'yo, RIKEN

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