1. Atsushi Tokiyasu (for LEPS collaboration) Experimental Nuclear and Hadronic Physics Laboratry, Department of Physics, Kyoto University

2. strangeness in nuclei 2013/2/13 GCOE Symposium @ Kyoto University1 / 11 ds us, SU(3) octet baryonSU(3) nonet meson  ? Hyper nuclei Shrinkage  impurity effect. nuclear force in SU(3) Kaonic nuclei new form of the nuclei whether exist or not? What happens in nuclei? uds hyperon kaon

3. dependent on the models of KN interaction the calculation methods. Formation of Cold (T=0) and Dense  > 2  0 ) nuclei. 2013/2/13 GCOE Symposium @ Kyoto University2 / 11 K can be bound in the nuclei by strong interaction. K N interaction (I=0) is strongly attractive ! X-ray shift of Kaonic Hydrogen K - p scattering data 2-body: KN :  (1405) ? 3-body: KNN : lightest nucleus. K - pp  the strongest bound state in 3-body systems Theoretical prediction (All theory support the existence) B.E. = 20-100 MeV  = 40- 110 MeV If  > B.E, it is difficult to observe experimentally. Ref: Particle Data Group Kaonic nuclei

4. Experiments 2013/2/13 GCOE Symposium @ Kyoto University3 / 11 FINUDA @ DA  NE (2005) DISTO@ SATURNE(2010) stropped K - on ( 6 Li, 7 Li, 12 C, 27 Al and 51 V) p p   p K + B.E. =  = invariant mass (  + p)Missing mass (   ) MeV M.Agnello, Nagae and Fujoka et al., PRL 94, 212303 (2005)T.Yamazaki et al., PRL 104, 132502 (2010) K - pp   p,   p,   n (non-mesonic decay)  easy to identify experimentally   p  (mesonic decay)

5. Summary of the introduction K - pp is the lightest kaonic nuclei. Existence of K - pp is not established. Experimental search using different reactions are awaited! Forthcoming experiments 3 He(K -, n)X  E15 @ J-PARC D(  +, K + )X  E27 @ J-PARC  D  K +  - X  LEPS @ SPring-8 2013/2/13 GCOE Symposium @ Kyoto University4 / 11  Prof.Nagae’s talk

6.  D  K +  - X reaction 2013/2/13 GCOE Symposium @ Kyoto University5 / 11 K+K+ --  “K” exchanged in t-chanel  unique for  -induced reaction  ( J = 1)  polarization observables are available. K - pp is “soft” object.  small momentum transfer  detect K + and  - at forward angle Search for a bump structure in the missing mass spectrum M x 2 = (E  + M D – E K - E  ) 2 - (p  – p K - p  ) 2  independent of decay chanel. K, K* Y* p n p K-K- p (E , p  ) (E , p  ) (E , p  ) (M D,0) Y* door-way.

7. SPring-8 “Super Photon ring-8 GeV” 2013/2/13 GCOE Symposium @ Kyoto University6 / 11 Data take: 2002/2003, 2006/2007  7.6 x 10 12 photons on LD 2 target SPring-8: 8 GeV electron storage-ring LEPS : hadron physics using  beam Back-word Compton Scattering e e Detect with Tagging counter E  =1.5 - 2.4 GeV experimental hatch  355nm laser 8 GeV LEPS  E  =12 MeV

8. LEPS spectrometer 2013/2/13 GCOE Symposium @ Kyoto University7 / 11 TOF Dipole Magnet 0.7 [Tesla] Target Start Counter DC2DC3 DC1SVTX AC(n=1.03) SSD (SVTX) Drift Chamber (DC 1~3) position Start Counter (SC) Time of flight wall (TOF) time Aerogel Cherencov counter (AC) Start Counter (SC) trigger   GeV  -- K+K+

9. particle identification 2013/2/13 GCOE Symposium @ Kyoto University8 / 11 K+K+ --  p/p ~ 6 MeV/c @ 1 GeV/c TOF (Time of flight) m 2 = p 2 (1/β 2 - 1) line tracking + Runge-Kutta method. mass p = 938.3 MeV mass K + = 493.7 MeV mass  - = 139.6 MeV c.f. p ++ K-K- 0

10. Missing Mass Spectrum 2013/2/13 GCOE Symposium @ Kyoto University9 / 11 Error Bar : statistical uncertainty (~5%) Red Box : systematic uncertainty (~20%) Hatched : discrepancy between datasets (~12%) preliminary No bump structure was observed!  upper limit of cross section   n search region: Mass = 2.22 - 2.36 GeV/c 2 B.E. = 150 - 10 MeV acceptance was corrected with Monte-Carlo simulation expected signal

11. Upper Limits of differential cross section 2013/2/13 GCOE Symposium @ Kyoto University10 / 11 preliminary -  = 20 MeV 0.05 - 0.25  b -  = 60 MeV 0.15 - 0.6  b -  =100 MeV 0.15 - 0.7  b a few % of typical hadron production cross section.  N   K  b   N   K  b  B.E.  15 points (10-150 MeV)   3 points upper limits of cross section were determined log likelihood ratio method

12. Conclusion and future prospect The existence of Kaonic nuclei is not established. K - pp was searched for using  D  K +  - X reaction No bump structures were found, and the upper limits of differential cross section were determined to be a few % of typical hadron production cross section. Future prospect detect the decay products from K - pp.  increase S/N search for other charge states using  D  K + K - pn,  D  K +  + K-nn 2013/2/13 GCOE Symposium @ Kyoto University11 / 11

13. Collaborators 2013/2/13 GCOE Symposium @ Kyoto University12 / 15

14. Appendix 2013/2/13 GCOE Symposium @ Kyoto University13 / 15

15. Appendix Merit deuteron  small nuclear effect(FSI). additional  - emission reduce the momentum transfer. K can be exchanged. polarization observable is available. Demerit small cross section (~nbarn). many background source limited information on hadron resonance. necessary to detect the decay product. 2013/2/13 GCOE Symposium @ Kyoto University14 / 15

16. Calculation of Upper Limits 2013/2/13 GCOE Symposium @ Kyoto University15 / 15 preliminary Upper Limit was calculated with log Likelihood ratio method Background proces  p  K +  -   p  K +  -   p  K +  -  (1385)  p  K +  -  (1385)-  p  K +  -  constant offset Signal Breit Wigner distribution -2  lnL = 3.841  upper limit (95% C.L.) Signal Yield

17. Theoretical calculation 2013/2/13 GCOE Symposium @ Kyoto University16 / 15 Binding EnergyDecay Width Method Yamazaki and Akaishi48 MeV61 MeVPhenomenological Variatioal Method Dote, Hyodo and Weise20±3 MeV40-70 MeVChiral SU(3) Variational Method Ikeda and Sato60 – 95 MeV45 - 80 MeVChiral SU(3) Fadeev Calculation Shevchenko, Gal and Mares 50 – 70 MeV90 – 110 MeVPhenomenological Fadeev Calculation S. Wycech and A. M. Green 56.5~78 MeV39~60 MeV Uchino, Hyodo and Oka depend on  * N Variational Method All calculations predict that K - pp can exist!! However… B.E. = 20 – 100 MeV  = 40 – 110 MeV Depending on the K N interaction model and Calculation Method.

18. Background processes 2013/2/13 GCOE Symposium @ Kyoto University17 / 15 preliminary 15 quasi- free processes were considered for fitting.  N  Y K+ Y K+  - Y* K+  - Y K+  -  The main background (~20 %)  n  K +  (1520)      N  K +  - X MM(K + ) MM(K +,  - ) MM(K + ) MM(K +,  - )   /ndf ~ 1.3 Y hyperon (  ) Y* hyperon resonance (  …)