A search for strange tribaryonic states

1
A search for strange tribaryonic states
in the reaction
Heejoong Yim Seoul National University For
KEK-PS E549 collaboration
2
KEK-PS E549 Collaboration

• H. Bhang, J. Chiba, S. Choi, Y. Fukuda, T.
  Hanaki, R. S. Hayano, M. Iio, T. Ishikawa, M.
  Iwai, S. Ishimoto, T. Ishiwatari, K. Itahashi, M.
  Iwasaki, P. Kienle, J. Kim, Y. Matsuda, H.
  Ohnishi, S. Okada, H. Outa, M. Sato, S. Suzuki,
  T. Suzuki, D. Tomono, E. Widmann, T. Yamazaki, H.
  Yim

3
Embedding K in nucleus?
Deep!
100 MeV
cf BN 10 MeV
Narrow!
20 MeV
meta-stable
Shrink!
high density?
4
How to produce?
Missing mass measurement
4He
Z 1 T 0 or 1
n
p p n K-
predicted
unpredicted
Z 0 T 1
p
p n n K-
3
5
Motivation of E549 Neutron Measurement
E471 nucl-ex/0310018
Possible states of the reaction
Reaction Z T TZ
0 1 -1 Next talker
1 1,0 0 Predicted by Akaishi
Due to low statistics Hard to confirm the
structure
Neutron spectrum
spectroscopy
Aim of
Search for state (T0) with
1 order higher statistics than E471
6
Overview of Experiment Setup
Stopped K- method. - 3 coincidence is required. ?
Incident K- and its track by beamline
detectors (K-/p- ratio 1/200, K-
5000/spill) ? Neutron and its stop
timing(TOF) by NC ? Secondary charged particle
and its track by TC-Tracking Chamber
Same condition with previous experiment
(Semi-Inclusive condition)
TC
?
?
NC
T0 BDC
VDC
?
TC
7
TOF for Neutral Events
Beam
Track viewed by VDCBDC

• TT0 Measured time by T0
• Tkaon_flight Beam (K-) flight time from T0 to
  its stop
• TNC Measured time by NC

TT0
TNC
veto
Tkaon_flight
TOF target?NC
Liq. He
TOFtarget?NC Flight time from target vertex to
NC
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Time Calibration and Resolution for Neutron
Counter (NC)
E471
E471
E threshold7 MeVee
1/ß
s0.030
E549
Preliminary
ADC (MeVee)
1.5 times Improved Missing Mass Resolution
1/ß
9
Check of TOF Analysis
Threshold2MeVee
S decay 1/ß 5.18
1/ß
ADC (MeVee)
Threshold2MeVee
S decay Pn 185MeV/c
Counts / (5 MeV/c)
MeV/c
Neutron momentum
Momentum scale and slewing correction are well
tuned
10
Background Level Check
E549
E471
5 MeVee
Counts/0.025
1/ß
10 MeVee
Counts/0.025
1/ß
Much improved S/N ratio ThresholdE471 10
MeVee ThresholdE549 7 MeVee
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Semi-Inclusive Neutron Spectrum
E471 (nucl-ex/0310018)
E549
Semi-inclusive
Semi-inclusive
Counts / (10 MeV/c)
Preliminary
Neutron momentum (MeV/c)
Neutron momentum (MeV/c)
About 8 times higher statistics
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Missing Mass Spectrum
Semi-inclusive neutron
To estimate upper limit of formation of kaonic
tribaryon state, pion coincidence is necessary.
Estimation with proton coincidence is difficult
in simulation, due to uncertainty of decay
mechanism of kaonic states.
Background subtracted
Very Preliminary
At the this stage, the narrow (G20 MeV/c2)
structure wasnt observed.
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Missing mass spectrum with pion coincidence
Efficiency corrected Missing Mass
Missing Mass
Neutron detection efficiency estimation by DEMON
code 1
Black 7 MeVee threshold Red 10 MeVee
threshold Blue 13 MeVee threshold
Very Preliminary
Arbitrary Unit
Counts/(5MeV/c2)
Efficiency ratio
Missing Mass MeV/c2
1 R. C. Byrd et al. Nucl. Inst. Meth. A313
(1992) 437.
Missing Mass MeV/c2
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Further analysis procedure

• Develop a simulation for the pion coincidence.
• Estimate number of stopped kaon in the target.

Goal at this stage
Obtain upper limit of the formation of the
tribaryon state.
The further analysis is in progress !
15
Summary

• Neutron spectra was measured for
  the reaction with upgraded
  setup.
• At this analysis stage, Narrow (G20 MeV/c2) peak
  structure did not appear on present result.
• Further analysis is in progress for the search
  for kaonic tribaryon state.