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Search for Exotic Hadrons, H-dibaryon resonance and Pentaquark

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 - ,K + LL ) reaction Pentaquark, Q + , by p - p -> K - Q + Summary. LL -Enhancement by the KEK-E224.

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Search for Exotic Hadrons, H-dibaryon resonance and Pentaquark

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  1. 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-,K+LL) reaction • Pentaquark, Q+, by p- p -> K-Q+ • Summary

  2. LL-Enhancement by the KEK-E224 J.K.Ahn et al., Phys. Lett. B444,267(1998) (1) H-dibaryon Resonance? K-p->X-K+; X-(p) -> H, H->LL (2) Strong LL Final State Interaction?

  3. Can we understand Consistently ? 6HeLL DBLL~1.01 MeV

  4. M.Hyata, H.Sato a) J.Asai, M.Kurosawa b) M.Kurosawa b) M.Ieiri, H.Takahashi c) , B.H.Choi g)

  5. - SCIFI active target 20 cm

  6. Performances / Results 151 events, 12C(K-,K+LLX) Analyzed 214

  7. Real Data Simulation Data

  8. LL-Invariant Mass S~ 9 s to the Combinatorial S~3 s to the INC+fss2(QCM) fss2 well reproduce BLL(6LLHe)~ 1. MeV

  9. 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)

  10. 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

  11. Missing mass spectrum of (+,K+) reaction • Inverse reaction of (-,K-) • Observe + peak

  12. 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

  13. Width fix Fitting of spectrum • Peak position • Width • Counts 182.570.8(stat.) 9.9(syst.) • Statistical significance 2.5~2.7 • Upper limit of peak count N < 298.3(90% C.L.)

  14. 1.92GeV/c CH2 target  < 4.1b(90% C. L.) 1.87GeV/c CH2 target  < 2.3b(90% C. L.) SCIFI targert  < 2.5b(90% C. L.) Assume s-wave  10.8% of K accepted Upper limit of cross section • fbeam=83%(e, contamination 13%,  reaction 4%) • eK2=72.3% • eDAQ=94% • fKabs=89.8% • etrack=84.6% • fdecay=57.6% • fcherenkov=91% • eMT=95.7% • eana=51% • d=0.14sr

  15. Conclusion 2 • We have searched for Pentaquark Q+ by p- p -> 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))

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