Production of Double Strangeness Hypernuclei in 12 C(K - ,K + ) Reaction at 1.67 GeV/c

1. Production of Double Strangeness Hypernuclei in 12C(K-,K+) Reaction at 1.67 GeV/c Choi Bong Hyuk Pusan National University For the E522 collaboration

2. Double Hypernuclei Double Hypernuclei Data Analysis Production of X Hypernuclei summary outlook Ξ- absorption (K-,K+) reaction

3. Theoretical prediction Double Hypernuclei Data Analysis Production of X Hypernuclei summary outlook H.Maekawa -> DWIA+LOFAt(Local Optimal Fermi Averaging t-matrix) Y.Yamamoto -> DWIA (Distorted wave impulse approximation ) Woods-Saxon Potential V0Ξ=-15MeV W0Ξ= 1MeV pΞ sΞ H.Maekawa et al. Eur.Phys.J 33, 269-272(2007) Y.Yamamoto et al. Prog.Theor.Phys.Suppl.117(1994)

4. Previous experiment Double Hypernuclei Data Analysis Production of X Hypernuclei summary outlook E224 E885 E224, E885 result Potential well depth ~ 14MeV : ( Woods-Saxon potential)

5. E522 Experiment Setup Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook 1.67GeV/c K- beam Image data Measurement Hypernuclei decay in SCIFI

6. Outgoing particle mass Double Hypernuclei Data Analysis Production of X Hypernuclei summary outlook Reconstructed mass distribution Cut condition -mass2-momentum cut -vertex cut -FTOF hit position cut -DChit- ToF cut π+ & proton are contaminated

7. Background rejection Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook above 1.15 GeV/c σ = 36.6 ± 3.6 MeV/c2 σ = 72.2 ± 2.0 MeV/c2 2 σ : 19.9 % 3 σ : 7.9 % 3 σ 2 σ

8. Background rejection Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook Dotted line : before π+ and p contamination cut Solid line : after π+ and p contamination cut Carbon event Image data (Carbon + Hydrogen) event Hydrogen event

9. Image data Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook Image Categorization

10. Coplanarity angle Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook cut position : -1° ~ 1° Hydrogenevent : 80.4% Carbonevent : 19.6%

11. p(K-,K+) missing mass distribution Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook For Hydrogen target |Ψ| < 1 p(K-,K+)X missing mass distribution K+ momentum distribution 19.4% carbon events σ = 14.5 MeV/c2

12. 12C(K-,K+) event Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook Quasi-free Ξ- Excitation Energy [MeV] Excitation Energy [MeV] no peak structure  QF Ξ- Quasi-free Ξ- event selection in the Image data • one prong events at reaction point • one prong and one kink at the prong • one prong stop in the SCIFI • one prong and several kink at the prong

13. 12C(K-,K+) event Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook Excitation energy spectrum with QF Ξ- function (Excitation energy spectrum) - (QF Ξ- function) count count Excitation Energy [MeV] • Solid line • obtained by QF Ξ- distribution below 0 MeV 47 events QF Ξ- function 17.27 Excitation Energy [MeV] Image check Decay mode check

14. Decay mode of 12ΞBe Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook Non-Mesonic decay : Ξ interact with bound nucleon  No charged particle at vertex Mesonic decay : Ξ decay inside the nucleus

15. Production Cross-section Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook Some QF-Ξ- events Excitation Energy [MeV]

16. Production Cross-section Double Hypernuclei Data Analysis 12C(K-,K+)X reaction summary outlook 90%confidence level upper limit Below 0 MeV < 1.714 μb/sr Excitation Energy [MeV]

17. Summary Data Analysis 12C(K-,K+)X reaction Double Hypernuclei Summary • (K-,K+) reaction investigate at KEK-PS K2 beamline • E522 spectrometer mass resolution •  14.5 MeV • Decay mode of 12ΞBe (below 0 MeV) • - ratio of mosonic decay to total event : 0.7 • - ratio of mesonic decay to non-mesonic decay : 2.5 • Production cross section • 90% confidence level upper limit •  < 1.714 μb/sr below 0 MeV

18. Thank you for your attention!!!