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Hiroaki Ohnishi RIKEN For the J-PARC E15 collaboration A search for deeply bound kaonic nuclear states by in-flight 3 He(K -,n) reaction ストレンジネスとエキゾティクス・理論の課題 March 1-3 2007 Toba
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A search for deeply bound kaonic nuclear states Direct production of K-pp cluster via 3 He(K-,n) reaction Direct production of K-pp cluster via 3 He(K-,n) reaction K-K- 3 He K - pp cluster neutron reaction Missing mass spectroscopy ??? Decay? Goal for the experiment J-PARC E15 Goal for the experiment J-PARC E15 To answering the basic question : whether the deeply bound state really exists? To answering the basic question : whether the deeply bound state really exists?
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Possible K - pp decay mode K - pp cluster FINUDA fit region K - pp?? Phys. Rev. Lett. 94, 212303 (2005) Invariant mass reconstruction +-p+-p -+p-+p K - pp 2370 MeV 2275 MeV 2267 MeV 0p0p pp 2131 MeV 2054 MeV p p -- p decay mode Dominant Decay mode = YN p p -- p decay mode B.E. = 115 MeV
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3 He(K-,n) reaction Formation of K - pp via 3 He(K-,n) reaction K-K- 3 He K - pp cluster neutron Missing mass reaction decay This mode allows us to investigate K-pp cluster with both missing mass and invariant mass spectroscopy p p -- Only charged particles in final state Invariant mass
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Detector concept Missing mass spectroscopy with forward going neutron Bound state tagging with the measurement of decay product –Good charged particle detection efficiency –Good charged particle momentum resolution K- beam momentum used for the experiment 1 GeV/c In the case, if B.E. = 100 MeV ( FINUDA case) Momentum of outgoing neutron will be 1.3 GeV reconstruction will be crucial for this measurement
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E15 Detector Experiment will be performed at K1.8BR beam line. Neutron counter Cylindrical detector system CDH CDC Solenoid Magnet K-K- Proton GEANT4 detector simulation B.E. = 100 MeV
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Expected decay mode for K-pp –K-pp ➾ Λp ➾ pπ-p – K-pp ➾ 0 p ➾ Λp ➾ pπ-p Assume K-pp = 60 MeV Invariant mass of Λp (MeV) ∑ channel Λ channel Expected detector performance p p -- p decay mode p p -- p decay mode
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Possible K - pp decay mode(2) +-p+-p -+p-+p K - pp 2370 MeV 2275 MeV 2267 MeV 0p0p pp 2131 MeV 2054 MeV Back to the beginning Akaishi-Yamazaki prediction based on (1405) as KN bound state Y.Akaishi & T.Yamazaki, PLB 535(2002) 70. Question BR( K-pp → p) BR( K-pp → YN) 1) Can we identify K-pp bound state only from missing mass? = ??? In this case, K-pp can be decay to mode pp nn pp pp pp YN mode 0p0p pp + 2) How to tag formation of K-pp bound state via decay product? Hyperon production
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Concerning on the decay mode of K - pp → p Can we use + - from target region as a tag of decay ? mode pp nn pp pp pp K - pp decay mode pp n p n n from decay p ++ -- -- ++ n from decay n proton cannot escape from target Still need to investigate
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Summary J-PARC E15 experiment 3 He(K-,n) reaction –Search for simplest deeply bound kaonic nuclear state, K - pp bound state via 3 He(K-,n) reaction Detector construction is in progress Experiment will be ready before Dec. 2008
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Λ Λ momentum (MeV/c) momentum (MeV/c) K - pp state σ ( MeV ) Expected decay mode for K-pp –K-pp ➾ Λp ➾ pπ-p – K-pp ➾ 0 p ➾ Λp ➾ pπ-p Assume K-pp = 60 MeV Invariant mass of Λp (MeV) ∑ channel Λ channel Expected detector performance p p -- p decay mode p p -- p decay mode
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