1. A search for deeply-bound kaonic nuclear states by in-flight 3 He(K -,n) reaction at J-PARC Hiroaki Ohnishi RIKEN Nishina Center J-PARC E15 experiment S. Ajimura, G. Beer, H. Bhang, P. Buehler, L. Busso, M. Cargnelli, J. Chiba, S. Choi, C. Curceanu, D. Faso, H. Fujioka, T. Fukuda, Y. Fukuda, C. Guaraldo, T. Hanaki, R. S. Hayano, A. Hirtl, M. Iio, M. Iliescu, T. Ishikawa, S. Ishimoto, T. Ishiwatari, K. Itahashi, M. Iwasaki, P. Kienle, J. Marton, Y. Matsuda, Y. Mizoi, O. Morra, T. Nagae, H. Ohnishi, S. Okada, H. Outa, A. Sakaguchi, M. Sato, M. Sekimoto, D. Sirghi, F. Sirghi, S. Suzuki, T. Suzuki, H. Tatsuno, D. Tomono, A. Toyoda, E. Widmann, T. Yamazaki, H. Yim, and J. Zmeskal

2. Search for Kaonic nuclear bound state Phys. Rev. Lett. 94 212303 (2005) Taken from OHP at Trento WS 2006 KEK E549 FINUDA KEK E548 Taken from OHP at Trento WS 2006 GSI FOPI What we need to answer the basic question, whether the deeply bound state really exists? The situation is still controversial! OBELIX Results of invariant mass analysis from E549 will be presented in INPC2007 conference by Dr. T. Suzuki

3. What we want to do ? Back to the original question Back to the original question Structure inside  (1405) Structure inside  (1405) multiquarks state? multiquarks state? Double pole resonance ? Double pole resonance ? bound state of K - p ? bound state of K - p ? Existence of K-pp bund state Will open new door to the physics of K-cluster If we assume  (1405) to be a K - p bound state If we assume  (1405) to be a K - p bound state Second simplest bound state, K - pp, will also exist ( natural extension) Second simplest bound state, K - pp, will also exist ( natural extension)

4. A search for deeply bound kaonic nuclear states Direct production of K-pp clusters via 3 He(in-flight K -,n) reaction Direct production of K-pp clusters via 3 He(in-flight K -,n) reaction 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? K-K- 3 He K - pp cluster neutron Missing mass Spectroscopy via neutron Reaction Decay ???

5. Possible K - pp decay modes 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 0p0p pp 2131 MeV 2054 MeV  p p --    p decay mode Dominant Decay mode = YN B.E. = 115 MeV K - pp cluster  p p --  p decay mode

6. Experimental Principle 3 He(K -,n) reaction 3 He(K -,n) reaction K-K- 3 He K - pp cluster neutron Missing mass Spectroscopy via neutron Reaction This mode allows us to investigate K-pp bound state in both Missing mass spectroscopy and Invariant mass reconstruction  p p -- Mode to decay charged particles Decay Invariant mass reconstruction

7. Signals from K - pp and “Two nucleon absorption” forward neutron K-K- 3 He reaction 3 He(K-,n) K - pp formation 3 He(K-,n) K - pp formation neutron K - pp cluster @ 1GeV/c K- and B.E. = 100 MeV ~ 1.3 GeV/c Two nucleon absorption Two nucleon absorption reaction K-K- 3 He neutron p (spectator)  @ 1GeV/c K- ~ 1.5GeV/c

8. How was decay side? K-K- 3 He reaction 3 He(K-,n) K - pp formation 3 He(K-,n) K - pp formation Two nucleon absorption Two nucleon absorption reaction K-K- 3 He Major background, i.e. event from “two nucleon absorption process” can be identified! neutron K - pp cluster  p p -- neutron p (spectator)   p -- Binding energy assumed as １００ＭｅＶ => emitted proton momentum ～ 500 MeV/c

9. Design for the experiment

10. Beam Line at J-PARC K1.8BR Beam Line K1.8BR Beam Line Design for low momentum Kaon (<1.2 GeV/c ) Design for low momentum Kaon (<1.2 GeV/c ) Single ES stage Single ES stage Beam line length = 27.6m Beam line length = 27.6m Primary Proton beam ES Q7 D4 Q8 FF Beam Spectrometer QDQ to focus at Final Focus (FF) QDQ to focus at Final Focus (FF) Momentum resolution ~ 2x10 -4 (position resolution of the beam tracker assumed to be 200  m (  ) ) Momentum resolution ~ 2x10 -4 (position resolution of the beam tracker assumed to be 200  m (  ) )

11. E15 Detector concept 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

12. Expected decay mode for K-pp Expected decay mode for K-pp K-pp ➾ Λp ➾ pπ-p K-pp ➾ Λp ➾ pπ-p K-pp ➾  0 p ➾  Λp ➾  pπ-p K-pp ➾  0 p ➾  Λp ➾  pπ-p Assume  K-pp = 60 MeV Assume  K-pp = 60 MeV Invariant mass of Λp (MeV) ∑ 0 channel Λ channel Expected detector performance  p p --  p decay mode  p p --    p decay mode

13. Status of the preparation

14. Neutron counter We will use same neutron counter used for KEK E549 experiment ( exist! ) We will use same neutron counter used for KEK E549 experiment ( exist! ) 20x5x150 cm 3 （ W Ｘ T Ｘ L ） Plastic scintillator Configuration16 (wide) x 7 (depth) Surface area3.2m X 1.5m 3.2 m 1.5 m E549 neutron counter

15. Solenoid magnet Solenoid magnet for E15 experiment has been constructed. Field strength;upto 0.7T Space inside;Φ=1.2m, L=1.2m weight ;23 t

16. Cylindrical Drift Chamber Design work for CDC is in progress Design work for CDC is in progress He based chamber gas will be used (to reduce material budget) Basic concept ; Cell structure has been chosen as Hexagonal 1800 readout channels in total 15 readout layers AA ’ A UU ’ VV ’ AA ’ UU ’ VV ’ AA Garfield simulation done by Dr. F. Sakuma

17. 3He target cell 3He heat exchanger 1 K tank(1.25 K) 4 K pot(4 K) LN2 tank Prototype 3 He target cell Target system R&D work for Liquid 3 He target is in progress ( Dr. S. Ishimoto (KEK) and Dr. M. Iio (RIKEN) )

18. Event rate estimation Parameters Parameters Assume production cross section as  3He(K-,n)K-pp = 10  b/sr Assume production cross section as  3He(K-,n)K-pp = 10  b/sr Acceptance of Neutron counter = 30 msr Acceptance of Neutron counter = 30 msr Target thickness = 20cm, density = 0.080 g/cm 3 Target thickness = 20cm, density = 0.080 g/cm 3 Neutron detection efficiency = 30% Neutron detection efficiency = 30% Assume 1/3 of K-pp decay in to (  +p or   +p) Assume 1/3 of K-pp decay in to (  +p or   +p)  +p reconstruction efficiency in CDC = 47%  +p reconstruction efficiency in CDC = 47% Expected event rate Expected event rate 1.86x10 -9 per an incident K - 1.86x10 -9 per an incident K - Event rate per day Event rate per day 0.8x10 6 K- per 3.53s (0.7s flat top) 0.8x10 6 K- per 3.53s (0.7s flat top) 24475 spill per day = 1.96x10 10 K- per day 24475 spill per day = 1.96x10 10 K- per day ~ 50 events per day ~ 50 events per day We will expect about ~1500 events in a month !!!

19. Summary J-PARC E15 experiment J-PARC E15 experiment Search for simplest deeply bound kaonic nuclear state, the K - pp bound state, via the 3 He(K-,n) reaction Search for simplest deeply bound kaonic nuclear state, the K - pp bound state, via the 3 He(K-,n) reaction Detector construction is in progress Detector construction is in progress Solenoid magnet ;constructed Solenoid magnet ;constructed CDC; under real design CDC; under real design 3 He target; R&D 3 He target; R&D Other detectors;conceptual design completed Other detectors;conceptual design completed Experiment will be ready before Dec. 2008 Experiment will be ready before Dec. 2008

20. Thank you very much