Search for Exotic Hadrons, Hdibaryon resonance and Pentaquark

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Search for Exotic Hadrons, H-dibaryon resonance
and Pentaquark

• K.Imai (Kyoto Univ.)
• for KEK-PS E522 collaboration
• Introduction
• KEK-PS E522 experiment
• H-dibaryon resonance by C(K-,KLL) reaction
• Pentaquark, Q, by p- p -gt K- Q
• Summary

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LL-Enhancement by the KEK-E224
J.K.Ahn et al., Phys. Lett. B444,267(1998)
(1) H-dibaryon Resonance? K-p-gtX-K
X-(p) -gt H, H-gtLL



(2) Strong LL Final State Interaction?

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Can we understand Consistently ?

6HeLL
DBLL1.01 MeV



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M.Hyata, H.Sato a)
J.Asai, M.Kurosawa b)
M.Kurosawa b)
M.Ieiri, H.Takahashi c)


, B.H.Choi g)

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-
SCIFI active target
20 cm
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Performances / Results
214
151 events, 12C(K-,KLLX) Analyzed
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(No Transcript)
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Real Data
Simulation Data
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LL-Invariant Mass
S 9 s to the Combinatorial S3 s to the
INCfss2(QCM)
fss2 well reproduce BLL(6LLHe) 1. MeV

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Conclusion 1

• We have confirmed the peak near threshold in LL
  mass spectrum previously observed by E224 with
  higher statistics.
• The data can not be explained with final state
  interaction which is consistent with weak
  attractive LL binding energy determined from
  the mass of 6HeLL.
• The H-dibaryon resonance is a possible
  interpretation of the peak. More theoretical
  input is needed as well as experiments.
• Data Analysis was done by C.J.Yoon (Kyoto)

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Pentaquark search in KEK-PS E522

• Objectives of E522
• H-dibaryon resonance search via (K-,K) reaction
• Kaonic Nuclei search via (K-,p) reaction
• Q search via (p-,K-) reaction (as extra)

3days
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Missing mass spectrum of (?,K) reaction

• Inverse reaction of (?-,K-)
• Observe ? peak

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Missing mass spectrum of (??,K?)
P?1.87GeV/c
P?1.92GeV/c
CH2 data A bump around 1.53GeV/c2 Statistical
fluctuation?
SCIFI , CH2 data are combined No clear peak
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Fitting of spectrum

• Peak position
• Width
• Counts 182.5?70.8(stat.) ?9.9(syst.)
• Statistical significance 2.52.7?
• Upper limit of peak count N? lt 298.3(90 C.L.)

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Upper limit of cross section

• fbeam83(e,? contamination 13,
• ? reaction 4)
• eK272.3
• eDAQ94
• fKabs89.8
• etrack84.6
• fdecay57.6
• fcherenkov91
• eMT95.7
• eana51
• d?0.14sr

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Conclusion 2

• We have searched for Pentaquark Q by p- p -gt K-
  Q reaction at KEK-PS
• A peak of 2.6 s was observed at 1531 MeV.
• Upper limit of the production cross section was
  obtained to be about 4 mb which is smaller than
  most of theoretical calculations.
• (The analysis was done by K.Miwa (Kyoto))