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

1. A search for deeply-bound kaonic nuclear states by in-flight 3He(K-,n) reaction at J-PARC 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 Hiroaki Ohnishi RIKEN Nishina Center

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

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

4. 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 clusters via 3He(in-flight K-,n) reaction K-pp cluster neutron 3He K- Reaction Missing mass Spectroscopyvia neutron Decay ???

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

6. Reaction Decay This mode allows us to investigateK-pp bound state in bothMissing mass spectroscopy and Invariant mass reconstruction Experimental Principle • 3He(K-,n) reaction neutron 3He K-pp cluster K- Missing mass Spectroscopyvia neutron Mode to decay charged particles p L p- Invariant mass reconstruction p

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

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

9. Design for the experiment

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

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

12. Lp decay mode p S0 p decay mode L ∑0 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

13. Status of the preparation

14. Neutron counter • We will use same neutron counter used for KEK E549 experiment ( exist! ) E549 neutron counter 3.2 m 1.5 m 20x5x150 cm3（WＸTＸL） Plastic scintillatorConfiguration 16 (wide)x7 (depth) Surface area 3.2m X 1.5m

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 Garfield simulation done by Dr. F. Sakuma Basic concept ; • Cell structure has been chosen as Hexagonal • 15 readout layers AA’A UU’ VV’ AA’ UU’ VV’ AA • 1800 readout channels in total • He based chamber gas will be used (to reduce material budget)

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

18. Event rate estimation • Parameters • Assume production cross section as s 3He(K-,n)K-pp= 10 mb/sr • Acceptance of Neutron counter = 30 msr • Target thickness = 20cm, density = 0.080 g/cm3 • Neutron detection efficiency = 30% • Assume 1/3 of K-pp decay in to (L+p or S0+p) • L+p reconstruction efficiency in CDC = 47% • Expected event rate • 1.86x10-9 per an incident K- • Event rate per day • 0.8x106 K- per 3.53s (0.7s flat top) • 24475 spill per day = 1.96x1010 K- per day • ~ 50 events per day We will expect about ~1500 events in a month !!!

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

20. Thank you very much 