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 Toba

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?

Possible K - pp decay mode K - pp cluster FINUDA fit region K - pp?? Phys. Rev. Lett. 94, (2005) Invariant mass reconstruction +-p+-p -+p-+p K - pp 2370 MeV 2275 MeV 2267 MeV 0p0p pp 2131 MeV 2054 MeV  p p --    p decay mode Dominant Decay mode = YN  p p --  p decay mode B.E. = 115 MeV

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

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

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

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

Possible K - pp decay mode(2) +-p+-p -+p-+p K - pp 2370 MeV 2275 MeV 2267 MeV 0p0p pp 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 pp nn pp pp pp YN mode 0p0p pp + 2) How to tag formation of K-pp bound state via decay product? Hyperon production

Concerning on the decay mode of K - pp →  p Can we use  +  - from target region as a tag of  decay ?  mode pp nn pp pp pp K - pp decay mode pp     n p n n from  decay p ++ -- -- ++ n from  decay n proton cannot escape from target Still need to investigate

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

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