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

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

summary outlook Production of  Hypernuclei Data Analysis Double Hypernuclei Theoretical prediction Y.Yamamoto et al. Prog.Theor.Phys.Suppl.117(1994) Y.Yamamoto -> DWIA (Distorted wave impulse approximation ) Woods-Saxon Potential V 0 Ξ =-15MeV W 0 Ξ = 1MeV H.Maekawa et al. Eur.Phys.J 33, (2007) pΞpΞ sΞsΞ H.Maekawa -> DWIA+LOFAt(Local Optimal Fermi Averaging t-matrix)

Previous experiment E224E885 E224, E885 result Potential well depth ~ 14MeV : ( Woods-Saxon potential) summary outlook Production of  Hypernuclei Data Analysis Double Hypernuclei

Image data Measurement Hypernuclei decay in SCIFI ExperimentTargetTarget size(cm 3 )material KEK E224SCIFI target8×8×10(CH) n AGS E885diamond target8×1×5C KEK E373hybrid emulsion KEK E522SCIFI target10×10×20(CH) n 1.67GeV/c K - beam summary outlook 12 C(K -,K + )X reaction Data Analysis Double Hypernuclei E522 Experiment Setup

Outgoing particle mass Reconstructed mass distribution summary outlook Production of  Hypernuclei Data Analysis Double Hypernuclei Cut condition -mass 2 -momentum cut -vertex cut -FTOF hit position cut -DChit- ToF cut π + & proton are contaminated

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

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

Type Ⅰ Type Ⅱ Type Ⅲ Type Ⅳ Type Ⅴ 1.One prong at vertex point 2.One KINK at the end of prong 3.or ‘V’ topology 1.Only just one prong at vertex point 2. Stop or escape 3. or ‘V’ topology 1.two prongs or three prongs 2.many prongs 3. or ‘V’ topology 1. No prong at vertex point 2. or ‘V’ topology 1. Another all Image Image Categorization Image data summary outlook 12 C(K -,K + )X reaction Data Analysis Double Hypernuclei

Coplanarity angle cut position : -1° ~ 1° Carbon event : 19.6% Hydrogen event : 80.4% summary outlook 12 C(K -,K + )X reaction Data Analysis Double Hypernuclei

summary outlook 12 C(K -,K + )X reaction Data Analysis Double Hypernuclei p(K -,K + ) missing mass distribution For Hydrogen target |Ψ| < 1 K + momentum distribution 19.4% carbon events p(K -,K + )X missing mass distribution σ = 14.5 MeV/c 2

12 C(K -,K + ) event summary outlook 12 C(K -,K + )X reaction Data Analysis Double Hypernuclei no peak structure  QF Ξ - 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 Quasi-free Ξ - event selection in the Image data Quasi-free Ξ - Excitation Energy [MeV]

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

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

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

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

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

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