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On the nature of the lowest 1/2 - baryon octet and decuplet

On the nature of the lowest 1/2 - baryon octet and decuplet. Bing-Song Zou ( Institute of High Energy Physics, CAS, Beijing ) B.C. Liu, B.S. Zou, PRL96 (2006) 042002; PRL98 (2007) 039102 J.J.Xie, B.S.Zou, PLB649 (2007) 405 J.J.Xie, B.S.Zou, H.C.Chiang, arXiv:0705.3950. Outline：

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On the nature of the lowest 1/2 - baryon octet and decuplet

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  1. On the nature of the lowest 1/2- baryon octet and decuplet Bing-Song Zou ( Institute of High Energy Physics, CAS, Beijing ) B.C. Liu, B.S. Zou, PRL96 (2006) 042002; PRL98 (2007) 039102 J.J.Xie, B.S.Zou, PLB649 (2007) 405 J.J.Xie, B.S.Zou, H.C.Chiang, arXiv:0705.3950

  2. Outline： • Introduction • Strange properties of N*(1535) • Nature of N*(1535) and its1/2- octet partners • Role of D*(1620) in ppnK+S+ • Nature of D*(1620) and its1/2- 10-plet partner • Conclusion

  3. s n(udd) p(uud) △- △0 △+ △++ (uuu) (ddd) (udd) (uud) 0 (uds) + (uus) 0 *- *+ -(dds) I3 0 (uus) (dds) (uds) *- *0 (uss) (dss) -(dss) 0(uss) - (sss) 1. Introduction SU(3) 3q-quark model for baryons 1/2 + spin-parity 3/2 + Successful for spatial ground states ! Prediction m- 1670 MeV experiment m- 1672.45 0.29 MeV

  4. Evidence for components other than 3q in the proton Deep Inelastic Scattering (DIS) + Drell-Yan (DY) process `d –`u ~ 0.12 Garvey&Peng, Prog. Part. Nucl. Phys.47, 203 (2001) Meson cloud picture: Thomas, Speth, Weise, Oset, Brodsky, Ma, … | p > ~ | uud > + e1 | n ( udd ) p+ (`du ) > + e2 | D++ ( uuu ) p- (`ud ) > + e’ | L (uds) K+ (`su ) > … Penta-quark picture : Riska, Zou, Zhu, … | p > ~ | uud > + e1| [ud][ud]`d > + e’ | [ud][us]`s > + …

  5. An outstanding problem for the classical 3q model • Mass order reverse problem for the lowest excited baryons • uud (L=1) ½ - ~ N*(1535) should be the lowest • uud (n=1) ½ + ~ N*(1440) • uds (L=1) ½ - ~ L*(1405) • harmonic oscillator ( 2n + L + 3/2 ) hw • To understand the full baryon spectroscopy, it is crucial to • understand the lowest 1/2- baryon octet and decuplet first !

  6. From relative branching ratios of J/y p`N*  p (K-`L) / p (`ph) gN*KL /gN*ph /gN*pp ~ 2 : 2 : 1 2. Strange properties of N*(1535) B.C. Liu, B.S. Zou, PRL96 (2006) 042002; PRL98 (2007) 039102 Evidence for large gN*Nh’from g p  p h’ M.Dugger et al., PRL96 (2006) 062001

  7. BES Collaboration, H.B.Li, B.S.Zou, H.C.Chiang, G.X.Peng, J.X.Wang, J.J.Zhu, Phys. Lett. B510 (2001) 75

  8. N*(1535) in J/y p K-`L + c.c. Nx Nx Events/10MeV (Arbitrary normalization) PS, eff. corrected Nx BES, Int. J. Mod. Phys. A20 (2005)

  9. Evidence for large gN*KL frompp  p K+L Total cross section and theoretical results with N*(1535), N*(1650), N*(1710), N*(1720) B.C.Liu, B.S.Zou, Phys. Rev. Lett. 96 (2006) 042002 pp  p K+L Tsushima,Sibirtsev,Thomas, PRC59 (1999) 369, without including N*(1535)

  10. COSY-TOF data S. Abdel-Samad et al., Phys.Lett.B632:27(2006) Both FSI & N*(1535) are needed ! FSI N*(1650) etc. FSI vs N*(1535) contribution inpp  p K+L B.C.Liu & B.S.Zou, Phys. Rev. Lett. 98 (2007) 039102 (reply) A.Sibirtsev et al., Phys. Rev. Lett. 98 (2007) 039101 (comment)

  11. Evidence for large gN*KL from gp  K+L B. Julia-Diaz, B. Saghai, T.-S.H. Lee, F. Tabakin, Phys. Rev. C 73, 055204 (2006)

  12. G.Penner&U.Mosel, PRC66 (2002) 055212 Partial wave decomposition For the fit to SAPHIR92-94 Data Dashed line : 1/2 - Dot-dashed line : 3/2+ Shklyar,Lenske&Mosel, PRC72 (2005) 015210

  13. pp  ppf p- p  nf with FSI no FSI p-ex r-ex h-ex Evidence for large gN*Nf from p- p  nf & pp  ppf Xie, Zou & Chiang, arXiv:0705.3950 Evasion of OZI rule by N*(1535) !

  14. Evidence for small gN*KS frompp  p K+L/pp  p K+S0 A.Sibirtsev et al., EPJA29 (2006) 363 [2] P.Kowina et al., EPJA22 (2004) 293

  15. `q ½ - [ud] [us] u `q ½+ [ud] [ud] u S d `q `q }L=0 }L=1 u d u d 3. Nature of N*(1535) and its 1/2- octet partner Zhang et al, hep-ph/0403210 N*(1535) ~ uud (L=1) + e [ud][us]`s + … N*(1440) ~ uud (n=1) + x [ud][ud]`d + … L*(1405) ~ uds (L=1) + e [ud][su]`u + … N*(1535):[ud][us]`s  larger coupling to Nh, Nh’, Nf & KL, weaker to Np & KS, and heavier !

  16. The new picture for the 1/2-octet predicts： L* [us][ds]`s ~ 1575 MeV S* [us][du]`d ~ 1360 MeV X* [us][ds]`u ~ 1520 MeV

  17. J/y decay branching ratio * 104 `p D(1232)+ 3/2+ < 1 `S- S(1385)+ 3.1  0.5 `X+ X(1520)- 5.9  1.5 `p N*(1535)+ 1/2- 10  3 `S- S(1360)+ ? `X+ X(1530)- ? It is very important to check whether under the S(1385) and X(1520) peaks there are 1/2- components ? }SU(3) breaking }SU(3) allowed

  18. `S u S u `S S u u d d Weise, Oset et al: N*(1535) as K L-KS state, L*(1405) as KN state Pentaquark vs Meson Cloud More solid information on its coupling to KS and its 1/2- octet partner are needed !

  19. 4.Role of D++*(1620) in ppnK+S+ J.J.Xie, B.S.Zou, PLB649 (2007) 405 Why D++* ? uuu -- the most experimentally accessible system with 3 identical valence quarks -- suggested the color degree of freedom in 1960s Why D++* (1620) ? JP = ½ - -- The lowest excited uuu state with L=1 in classical 3q models

  20. K+ D*++ p S+ p +, r + p n Why ppnK+S+ ? Our present knowledge on D++* resonances mainly comes from p+p experiments and is still very poor. ppnK+S+ -- D++* production from r+p -- accessible at COSY and CSR

  21. -- New COSY-11 data Status on the study ofppnK+S+ Resonance model Incohenrent p/K exchange model also fails to reproduce these data

  22. D*++(1620) with r+ exchange D*++(1620) with p+ D*++(1920) with p+ exchange Our calculation forppnK+S+ t-channel r-exchange plays important role !

  23. 5. Nature of D*(1620) and its 1/2- 10-plet partner D*(1620)  ppN & ppnK+S+ extra-ordinary strong coupling of D*(1620) to rN  D*(1620) ½- rN molecule ? 1705 MeV S*(1750) ½- K*N molecule ? 1820 MeV X*(1950) ½-? K*L molecule ? 2010 MeV W*(2160) ½-? K*X molecule ? 2215 MeV 1/2- baryon decuplet ~ V8B8 molecules ?

  24. Conclusion `qqqqq in S-state seems more favorable than qqq with L=1 ! 1/2- baryon octet ~`qq2q2 state + … 1/2- baryon decuplet ~ V8B8 molecules + …

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