A search for deeply bound kaonic nuclear states by in-flight 3 He(K - ,n) reaction

1. 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 A search for deeply bound kaonic nuclear states by in-flight 3He(K-,n) reaction Hiroaki Ohnishi RIKEN For the J-PARC E15 collaboration

2. K-pp cluster neutron reaction A search for deeply bound kaonic nuclear states • Goal for the experiment J-PARC E15 • To answering the basic question : whether the deeply bound state really exists? • Direct production of K-pp cluster via 3He(K-,n) reaction 3He K- Decay? Missing mass spectroscopy ???

3. K-pp 2370 MeV K-pp cluster 2275 MeV p+S-p p-S+p 2267 MeV fit region Lp decay mode p S0 p decay mode L g K-pp?? p p- L FINUDA 2131 MeV S0p p- p Phys. Rev. Lett. 94 , 212303 (2005) p 2054 MeV Lp Possible K-pp decay mode Dominant Decay mode = YN B.E. = 115 MeV Invariant mass reconstruction

4. K-pp cluster neutron reaction Only charged particles in final state decay p L p- p Formation of K-pp via 3He(K-,n) reaction 3He K- Missing mass This mode allows us to investigate K-pp cluster with both missing mass and invariant massspectroscopy Invariant mass

5. 1 GeV/c Detector concept • Missing mass spectroscopy with forward going neutron K- beam momentum used for the experiment In the case, if B.E. = 100 MeV ( FINUDA case) Momentum of outgoing neutron will be 1.3 GeV • Bound state tagging with the measurement of decay product • Good charged particle detection efficiency • Good charged particle momentum resolution L reconstruction will be crucial for this measurement

6. Proton GEANT4 detector simulation CDH p- Proton CDC Solenoid Magnet K- B.E. = 100 MeV E15 Detector Experiment will be performed atK1.8BR beam line. Neutron counter Cylindrical detector system

7. Lp decay mode p S0 p decay mode L ∑ channel Λ channel g p p- L p- p p Invariant mass of Λp (MeV) Expected detector performance • Expected decay mode for K-pp • K-pp ➾ Λp ➾ pπ-p • K-pp ➾ S0p ➾ gΛp ➾ g pπ-p • Assume GK-pp= 60 MeV

8. Akaishi-Yamazaki prediction based on L(1405) as KN bound state In this case, K-pp can be decay to Hyperon production YN mode pS mode p0S0p S0p p+S0n Lp + p+S-p p0S+p p-S+p Possible K-pp decay mode(2) Back to the beginning K-pp 2370 MeV 2275 MeV p+S-p p-S+p 2267 MeV Y.Akaishi & T.Yamazaki, PLB 535(2002) 70. Question 2131 MeV S0p 1) Can we identify K-pp bound state only from missing mass? 2) How to tag formation of K-pp bound state via decay product? BR( K-pp → pSp) BR( K-pp → YN) 2054 MeV = ??? Lp

9. p-S+p p- p+n p n from S decay p K-pp decay mode n pS mode p0S0p p+ p+S0n p- p+S-p p0S+p p-S+p Concerning on the decay mode of K-pp →pSp • Can we use p+p- from target region as a tag of pS decay ? p- n from S decay n p+ proton cannotescape from target Still need to investigate

10. Summary • J-PARC E15 experiment • Search for simplest deeply bound kaonic nuclear state, K-pp bound state via 3He(K-,n) reaction • Detector construction is in progress • Experiment will be ready before Dec. 2008

11. Lp decay mode p S0 p decay mode L ∑ channel Λ channel g p p- L p- p p Invariant mass of Λp (MeV) Expected detector performance K-pp state Λ σ（MeV） σ（MeV） • Expected decay mode for K-pp • K-pp ➾ Λp ➾ pπ-p • K-pp ➾ S0p ➾ gΛp ➾ g pπ-p • Assume GK-pp= 60 MeV Λmomentum (MeV/c) momentum (MeV/c)