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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
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summary outlook
Production of Hypernuclei
Data Analysis
Double HypernucleiDouble
Hypernuclei
Ξ- absorption
(K-,K+) reaction
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summary outlook
Production of Hypernuclei
Data Analysis
Double HypernucleiTheoretical
prediction
Y.Yamamoto et al. Prog.Theor.Phys.Suppl.117(1994)
Y.Yamamoto -> DWIA (Distorted wave impulse approximation )
Woods-Saxon Potential
V0Ξ=-15MeV
W0Ξ= 1MeV
H.Maekawa et al. Eur.Phys.J 33, 269-272(2007)
pΞ
sΞ
H.Maekawa -> DWIA+LOFAt(Local Optimal Fermi Averaging t-matrix)
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Previous experiment
E224 E885
E224, E885 resultPotential well depth ~ 14MeV : ( Woods-Saxon potential)
summary outlook
Production of Hypernuclei
Data Analysis
Double Hypernuclei
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Image data
Measurement Hypernuclei
decay in SCIFI
Experiment Target Target size(cm3) material
KEK E224 SCIFI target 8×8×10 (CH)n
AGS E885 diamond target 8×1×5 C
KEK E373 hybrid emulsion
KEK E522 SCIFI target 10×10×20 (CH)n
1.67GeV/cK- beam
summary outlook
12C(K-,K+)X reaction
Data Analysis
Double HypernucleiE522
Experiment Setup
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Outgoing particle mass
21
pm
cT
L
Reconstructed mass distribution
summary outlook
Production of Hypernuclei
Data Analysis
Double Hypernuclei
Cut condition-mass2-momentum cut-vertex cut-FTOF hit position cut-DChit- ToF cut
π+ & proton are contaminated
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Backgroundrejection
pKabove 1.15 GeV/c
σ = 36.6 ± 3.6 MeV/c2
2 σ
2 σ : 19.9 %
summary outlook
12C(K-,K+)X reaction
Data Analysis
Double Hypernuclei
pKpK
3 σ
3 σ : 7.9 %
σ = 72.2 ± 2.0 MeV/c2
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Backgroundrejection
Dotted line : before π+ and p contamination cutSolid line : after π+ and p contamination cut
(Carbon + Hydrogen) eventCarbon event
Hydrogen eventImage data
summary outlook
12C(K-,K+)X reaction
Data Analysis
Double Hypernuclei
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Type Ⅰ Type Ⅱ Type Ⅲ Type Ⅳ TypeⅤ1.One prong at
vertex point2.One KINK at the
end of prong3.or ‘V’ topology
1.Only just one prong
at vertex point2. Stop or escape3. 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 datasummary
outlook
12C(K-,K+)X reaction
Data Analysis
Double Hypernuclei
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Coplanarity angle
cut position : -1° ~ 1°
Carbon event : 19.6%
Hydrogen event : 80.4%
summary outlook
12C(K-,K+)X reaction
Data Analysis
Double Hypernuclei
)(cos2
1 KK
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summary outlook
12C(K-,K+)X reaction
Data Analysis
Double Hypernucleip(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/c2
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12C(K-,K+) eventsummary
outlook
12C(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]Excitation Energy [MeV] Excitation Energy [MeV]Excitation Energy [MeV]
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12C(K-,K+) eventsummary
outlook
12C(K-,K+)X reaction
Data Analysis
Double Hypernuclei
Excitation energy spectrum with QF Ξ- function
Solid lineobtained by QF Ξ- distribution
(Excitation energy spectrum) - (QF Ξ- function)
Image check
below 0 MeV47 eventsQF Ξ- function17.27
Decay mode check
coun
t
coun
tExcitation Energy [MeV]Excitation Energy [MeV]
Excitation Energy [MeV]Excitation Energy [MeV]
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Decay mode of 12
ΞBe
summary outlook
12C(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
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ProductionCross-section
summary outlook
12C(K-,K+)X reaction
Data Analysis
Double Hypernuclei
angleacccoKKKK
fffd
d
d
d
),(C),(CBe 121212 N
N
Excitation Energy [MeV]Excitation Energy [MeV]
Some QF-Ξ- events
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summary outlook
12C(K-,K+)X reaction
Data Analysis
Double HypernucleiProduction
Cross-section
90% confidence level upper limit
Below 0 MeV< 1.714 μb/sr
Excitation Energy [MeV]Excitation Energy [MeV]
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Summary 12C(K-,K+)X reaction
Data Analysis
Double HypernucleiSummary
• (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
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Thank you for your attention!!!