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Pentaquark at KEK

K.Imai: Exotics 04/2/18 (Kyoto). Pentaquark at KEK. K.Imai (Kyoto) Introduction Width and spin-parity of Q + Proposed experiment at KEK-PS Summary. Discovery of Pentaquark Q +. M = 1540 10 MeV G < 25 MeV Gaussian significance 4.6 s. Renaissance of hadron spectroscopy !.

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Pentaquark at KEK

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  1. K.Imai: Exotics 04/2/18 (Kyoto) Pentaquark at KEK K.Imai (Kyoto) • Introduction • Width and spin-parity of Q+ • Proposed experiment at KEK-PS • Summary

  2. Discovery of PentaquarkQ+ M = 154010 MeV G < 25 MeV Gaussian significance 4.6s Renaissance of hadron spectroscopy ! background T. Nakano et al., Phys.Rev.Lett. 91 (2003) 012002

  3. Questions about Q+ Spin-parity: Jp= ½+ or ½- or 3/2 -> selection of models s-wave or p-wave ? K+n -> K+n phase shift analysis pol.g N -> K- Q+ decay distribution of Q+ angular dependence -> SPring-8 TPC project

  4. Only upper limit for width CLAS/JLAB DIANA/ITEP g d → p K+ K-n K+Xe → K0p X (K+n→ K0p) M = 15392 MeV G < 9 MeV M = 15425 MeV G < 21 MeV hep-ex/0304040 hep-ex/0307018

  5. CLAS/Jlab hep-ex/0307088 SAPHIR/ELSA hep-ex/0307083 M = 153710 MeV G < 32 MeV M = 153710 MeV G < 32 MeV M = 154042 MeV G < 25 MeV

  6. Question about width • upper limit from direct measurement: 9 (20) MeV • S.Nussinov (hep-ph/0307357) based on K+d scattering data G(Q+)<6MeV • Arndt,Strakovski & Workman (nucl-th/0308012) based on existing K+N elastic scattering data G(Q+) as small as 1 MeV

  7. High resolution spectroscopy of pentaquark Q+ (proposal to KEK-PS) • K.Imai, K.Miwa, M.Hayata, M.Miyabe, N.Muramatsu, M.Niiyama, N.Saito, M.Wagner, M.Yosoi (Kyoto U.) • T.Nagae, M.Ieiri, N.Noumi, Y.Sato, S.Sawada, M.Sekimoto, H.Takahashi, A.Toyoda (KEK) • H.Fujioka, T.Maruta (U. Tokyo) • T.Fukuda, P.K.Saha (Osaka ECU) • T.Nakano (RCNP) • K.Hicks (Ohio) • K+ p ->p+ Q+ reaction with SKS spectrometer at KEK K6 beam line • excellent mass resolution DE=1.0 MeV • Decay angular distribution for spin determination

  8. SKS spectrometer

  9. L12C hypernucleus with SKS Best energy resolution ∆E(FWHM)=1.45 MeV 2.0 MeV

  10. Missing mass resolution for K+p ->p+Q+

  11. Yield and background • Cross section: 80mb at P(K+)=1.2GeV/c ? (Y.Oh et al., hep-ph/0311054) • Yield: 3500/60shift • Background reactions (K+,p+) ( R.Bland et al., Nucl. Phys. B13 (1969) 595) • K+p -> K0D+(p+p) 3.4 +- 0.3 mb • K+p -> K+D+(p+n) 0.3 +- 0.1 mb • K+p -> K*(K0p+) p 1.1 +- 0.2 mb • K+p -> K0p+ p (3-body) 0.25 +- 0.30 mb • K+p -> K+p+ n (3-body) 0.24 +- 0.06 mb

  12. Simulation (width=0)

  13. Simulation (width=1MeV)

  14. Simulation (width=8MeV)

  15. Expected Statistical Significance (width vs cross section)

  16. Dalitz Plot

  17. E522 (KEK-PS) • Search for H-dibaryon resonance via 12C(K-,K+LL) and study of XN interactions C.J.Yoon tomorrow by-product ? Q+ search by p(p-,K-) Q+ at p(p-)=1.9 GeV/c (under analysis) No peak was observed in old BC data (poor statistics)

  18. Summary Penta-quark (Q+) needs further confirmation by hadron induced reactions. p- p ->K- Q+, K+ p ->p+ Q+, , , • Width and spin-parity must be determined • High resolution spectroscopy of Q+ is proposed with SKS spectrometer at KEK DE=1MeV ! • Decay angular distribution for spin assignment

  19. To establish anti-decuplet • X- - n K- -> K+X- - , p K- -> K+p+X- - • X+ p K- -> K0p- X+ S=-2 S=0 Diakonov 2070 1710 MeV Jaffe, Wilczek 1750 1440 MeV • If M(X--) ~ 1750 MeV (Jaffe & Wilczek, hep-ph/0307341) >2GeV/c K- beam (BNL or KEK or (J-PARC)) !

  20. S=-2 Penta-quark X-- NA49 collaborationM=1862 MeV G<18 MeVhep-ex/0310014 5.6s

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