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f meson in nucleus at J-PARC

New Frontiers in Q D C 2010 Exotic Hadron Systems and Dense Matter – Mini Symposium on Exotic hadrons Feb/23/2010. f meson in nucleus at J-PARC. phi meson production at JPARC. Hiroaki Ohnishi RIKEN. This talk is based on the submitted proposal to J-PARC. Introduction.

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f meson in nucleus at J-PARC

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  1. New Frontiers inQDC2010 • Exotic Hadron Systems and Dense Matter – • Mini Symposium on Exotic hadronsFeb/23/2010 f meson in nucleus at J-PARC phi meson production at JPARC Hiroaki Ohnishi RIKEN

  2. This talk is based on the submitted proposal to J-PARC

  3. Introduction

  4. My personal questions • What is the meaning of mass ? • What is the meaning of mass in nuclear media? • i.e. If mass reduction of vector meson exist, what is the meaning? • Is there any clear relationsbetweenChiral order parameter <qq>mass reduction of mesons in nuclear media

  5. f meson in nuclear media • why are we focusing on f meson? • Quark content : ~100% ss • Mass shift on f meson in nuclear matter is directly connecting (?) to the in medium change of strange quark condensate <ss> (or gluon condensate?)Direct access to the chiral symmetry restoration in the strangeness sector can be possible via f meson • f meson in nuclear media will give us unique information on strange content of nucleon and nuclear matter

  6. T. Hatsuda, H. Shiomi and H. Kuwabara Prog. Theor. Phys. 95(1996)1009 f mesons in nuclear media- theoretical situation • Mass of vector meson in nuclear media will be decreasing when density increasing (QCD Sum rule) (if no width broadening ?) • Very small mass shift but significant broadening of decay width (Chiral SU(3) ….) NPA 624(1997)527

  7. f mesons in nuclear media- experimental situation • mass shift (~3%) of f meson have been observed by KEK-PS E325.( with the width getting 3.6 times bigger then the width in vacuum) - PRL 98(2007)04501 • photo production of f meson from Li, C, Al, and Cu at LEPS/SPRING-8 • sfN in nuclear media getting much bigger (~35 mb) than in free space ( huge width broadening ) - PLB608(2005)215 ~2GeV/c • f meson production in 158 GeV/c In-In collisions at CERN/SPS (NA60) • mass shift and width broadeningare not identified in hot nuclear matter(within detector resolution) - EPJ C64(2009)1-18 What is really happening on f meson in nuclear media

  8. 2p G = 407 eV 1s DE = -323 eV -8.6 keV only Coulomb int. Considering mass reduction in nuclear media • Strong attractive force exist between KbarN This is confirmed by measurement of 2p->1s x-ray energy in Kaonic hydrogen atom M.Iwasaki et al., PRL78 (1997) 3067 • The strong attraction between KbarN lead to the conclusion of mass reduction of Kbar(K-)in nuclear media. Mass reduction = attractive force exist ??? = attractive potential ? Nucl.Phys.A617(1997)449

  9. f-N bound state? • f-N bound state has already been discussed in year 2000, however totally independent starting point. • Meson-Nucleon bound state with “QCD van der Waals” attractive force (Originally this idea is developed for the discussion of hc-N bound state) Binding energy obtained with this analysis is 1.8 MeV/n. Assume : BEA = BEN x A 2/3 ( like the case of hyper nucleus ) binding energy for Copper nucleus (for example) ~ 28 MeV.

  10. f-N bound state? • Results from Chiral SU(3) quark model Experiment to search for such bound state has been performed,(at CLAS),But no experimentally evidence for existence of such (quasi-) bound state

  11. Goal of the experiment • Question is how to measure mass shift which can be compared with theoretical prediction?? • the invariant mass study of f→ ee in nucleus • f-meson bound state • measurement of binding energy and width (J-PARC E16) (J-PARC P29) This part is missing!!! Origin of mass shift and contribution of chiral symmetry restoration in the mass of vector meson (need helps from theory..)

  12. Experimental method

  13. How to identify f meson bound state • Formation of f mesic nucleus will be identified with missing mass analysis. a b f • Need to find good elementary process for f meson production • (p,K) reaction for hyper nucleus formation • produced f meson momentum must be small (up to a few hundred MeV/c)

  14. How to produce f with low momentum efficiently? • f production via p(p,f)f reaction KEK-E325f mesonbg distribution • Momentum transfer ~ 200 MeV/c • Very interesting production process • Double f meson production will be dominant around threshold ( 0.9 GeV/c<p<1.4 GeV/c) • Only less than 10% physical background ~2GeV/c f meson production cross section will be smaller than KEK E325, but using pbar, could produce slow f meson efficiently • Once we detect one f meson in the reaction, partner will also be f meson • Missing mass spectroscopy can bedone with forward going f meson

  15. Huge BackgroundHowever, once one can identify third strangeness in the event, then event sample will be almost background free How to produce f with low momentum efficiently? f meson production with anti-proton will be primary candidate of the elementary process for the f mesoic-nucleus production.

  16. s s Φ K+ s u u s u u p Λ d d How to ensure f meson is really in nucleus • Let’s focusing on decay mode • Mass of the f meson will be decreasing about 30 MeV. • i.e. 1019 MeV – 30 MeV = 989 MeV ~ 2 x MKaonMain decay mode for Φmeson, Φ→K+K-, will be suppress. • However, Φ meson is in nucleus. There are many nucleon surrounding them. 1019 MeV – 30 MeV + 938 MeV(proton)　　　　　　　　　　　　　　　　　＝ 1927 MeV > MKaon+MΛi.e.Φp→K+Λ will be a dominant decay mode,if f meson is in nucleus. (This mode is not suppressed by OZI role ) i.e. K+L in final state will be a good signal to ensure f meson in medium

  17. Concept for the experiment Nuclear target Outgoingf meson f meson bound state Reaction Anti-proton Missing mass Spectroscopy Decay K+ Strangeness tag!! L

  18. Very recent theoretical progresson f mesic nucleus • Posibility of f mesic nuclei formation has beendiscussed in this paper, arXiv:1001.2235v1 [nucl-th] 13 Jan 2010 If attractive potential is strong enough,some hope to see the peak? Structuredue to the bound state formation…

  19. f uu du ud ss p ss p f Concerning for the experiment p f • pbar-p → ff reaction is really happeningin nucleus???? • f production process : • Direct production process • OZI rule viorated • Anomalous large cross section • This process can be expected even in nucleus. • Kaon loop • According to a theoretical calculation, Kaon loop process contributes 2mb to 4mb of cross section. • If such hadron loops are main component of ff production, its process may suppress in nuclear medium (??). • Theoretical calculation or experimental evidence is important. p f p f K K p f K Probably we need to measure cross section of pbar-p → ff in light nucleus as 1st step

  20. Detector conceptandsignal expected

  21. Antiproton Nucleus Experimental method How to produce and detect f mesic nucleus? L K+ Φ K+ Φ Slow f meson Bound Fast Φmeson K- ～0.3GeV/c ～１GeV/c Φmesic nucleus Missing mass using reconstructed forward going f coincidence with K+ and L from target Momentum of f produced by this reaction Just select fproduced to180°in CM If we choose pbar momentum = 1.0 – 1.3 GeV/cmomentum of the f will be 200 – 260 MeV/c

  22. Conceptual design of the detector Large acceptance forforward going f meson(for missing mass analysis) Main spectrometer • Large solid angle charged particle spectrometer (with large gap dipole magnet) Large solid angle for the decay particles, K+ and L, from f mesic nucleus CDC ToF wall Target Region K+ K- target beam Antiproton beam Target surrounded by trigger counter

  23. Candidate of spectrometer magnet Conceptual design of the detector • ToF wall = Resistive Plate Chamber (RPC) • FOPI ToF Wall will be a model • < 65 ps time resolution • Working well under the magnetic field Target Region target beam RIKEN 4th-cyclotron magnetnow used as historical monument 220 cm pole diameter • Aerogel cherenkov counter • n~1.2 will be used CDC

  24. Typical event display • p + Cu  f + fNi (Bf = 30 MeV) • “f”+”p”  K+ + L • ( proton & f at rest ) • All decay processes are isotopic. Y [cm] K- ~500 MeV/c K+ ~500 MeV/c Detector simulationusing GEANT4 based onconceptual detector designis in progress X [cm] K+ ~500 MeV/c p- ~100 MeV/c P ~450 MeV/c Y [cm]

  25. Anyway, how the signal looks like? • If life is simple enough (I knew life is complicated) • Assumption in the simulation: • bound state with 30 MeV B.E. exist • Spectrometer missing mass resolution = 18 MeV (s) • Fermi momentum in nucleus is taking into account in the simulation • Gf in nucleus assumed to be broaden 10 time more than natural width Blue triangle: Missing mass spectra of unbound fRed circle : Expected signals

  26. Summary • Based on the results reported by KEK-PS E325(mass shift of f meson) strongly suggested that the production of f mesic nucleus can be possible. • The most promising elementary process for the f mesic nucleus production will be pp→ff channel. • Naïve event rate estimation tells us that ~200 events candidate for f mesic nucleus will be produce per 40 days,with beam intensity, 1x106/spill, for 1.1 GeV/c anti-proton.

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