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S * production in g N K pL and Kp pL

BARYONS’10. S * production in g N K pL and Kp pL. Puze Gao Institute of High Energy Physics, CAS, China Collaborators: B.S. Zou, J.J. Wu, A.Sibirtsev 2010-12-10. Outline. Introduction S resonances Recent experiments Study on Analysis of Summary and conclusion.

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S * production in g N K pL and Kp pL

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  1. BARYONS’10 S* production in gN KpL and Kp pL Puze Gao Institute of High Energy Physics, CAS, China Collaborators: B.S. Zou, J.J. Wu, A.Sibirtsev 2010-12-10

  2. Outline • Introduction • S resonances • Recent experiments • Study on • Analysis of • Summary and conclusion S(1380)1/2-, others in PDG gN KS*KpL LEPS,CLAS KppL Crystal Ball Gao, Wu, Zou, PRC81,055203 (2010); Gao, Zou, Sibirtsev, arXiv: 1011.2387.

  3. Introduction ——S resonances • S resonances in PDG 4-star resonances: S*(1385)3/2+, S*(1670)3/2-, S*(1775)5/2- Others: 2-star 1560,1620,1-star 1480,1580,etc. • S(1380)1/2- Pentaquark picture predictsS(1/2- ) near 1380 MeV. Jaffe, Wilczekd, PRL91,232003(2003); Zhang, et.al., HEP&NP,29,250(2005); Helminen, Riska, NPA699,624(2002). S(1380) with JP=1/2-decays to Lp, may be buried inS*(1385). Some evidence: Wu, Dulat, Zou,PRD80,017503(2009); PRC81,045210(2010)

  4. Introduction ——recent experiments • g-N scatter: CLAS 2005： Eg=1.5-4 GeV NSTAR05, arXiv: 0601010 LEPS 2009： Eg=1.5-2.4 GeV PRL 102,012501 • K-N scatter: Crystal Ball 2009： PRC 80,025204 pK=514-750 MeV

  5. Study ong N KS* A. theoretical frame work • Feynman diagrams forgN -> KS*(3/2+) : K g N KpL N,D L,S*

  6. Effective Lagrangians forgN -> KS*(3/2+) : • Oh, Ko, Nakayama, PRC77,045204(2008) with

  7. where

  8. Y(1/2+)

  9. Form factors and contact current: t-channel K exc. Other channels The contact current for is • Haberzettl et. al, • PRC74,045202(2006) where

  10. The contact current for is where where h is a free parameter to fit experiments.

  11. B. Previous study vs. data • Total cross section of CLAS well described. • differential cross section of LEPS data also be described, but not for the beam asymmetry Abeam. • Hicks, et.al. (LEPS), PRL102,012501(2009)

  12. B. Our ideas a. including S(1380)1/2- • Feynman diagrams forgN -> KS*(1/2-) : K N S(1/2-),(L)

  13. effective Lagrangians： • Contact currents： where where

  14. B. Ideas b. Tuning parameter h in contact term for • Parameter h=1 is used in to describe the total cross section. • A different h for process seems necessary, if we do not include the S(1380)1/2-.

  15. C. Results and discussion • LEPS photon beam is linear polarized. • beam asymmetry Abeam defined as • Previous theoretical study predicts a very small Abeam • LEPS data gives a large negative Abeam (-0.4, -0.2)

  16. Previous study vs. data Our result forgn -> KS(1/2-) Thus with a portion ofKS(1/2-) produced, the negative Abeam can be explained.

  17. Include S(1380)1/2- Tune parameter h=1.11

  18. ds/dcosqc.m.for gn ->KS* compared with LEPS data

  19. Integrated cross section for gn->KS* vs. LEPS data II I differentpredictions for the two schemes. Scheme I describes both with same parameters, Scheme II shoud use different h . Integrated cross section for gp->KS* vs. CLAS data

  20. Analysis of Kp p L Crystal Ball 2009： pK=514-750 MeV Prakhov et al., PRC 80,025204 The high precision new data can give valuable information for S resonances. S resonances

  21. A. theoretical frame work • Feynman diagrams forKN -> pL: K* N S,S*, etc.

  22. effective Lagrangians： t-channel: u-channel:

  23. s-channel:

  24. Form factor：

  25. B. results • Differential cross sections for is calculated ： The 4-star S resonances as follows are always included With only t-, u- and the above 4 s-channels, the best fit of 17 tunable parameters gives c2 =245 for the 128 data points. Then we try to include some other S resonance, and two schemes can both give very low c2, scheme I: , scheme II:

  26. scheme I, with inclusion of S(1530)1/2+, c2 =78.2 for 128 data points. scheme II, with inclusion of S(1550)1/2-, c2 =78.3 for 128 data points, S(1550)1/2- seems like the S(1560) bump in PDG. For S(1380)1/2-, the present data is insensitive to it, and it is neither supported nor excluded.

  27. Summary • We study the reactions gN ->KS*->KpLand K-p ->p0Lby recent data to gain insight of the S resonances. • For gN ->KS*, including S(1380)1/2- is helpful to reproduce data with the same set of parameters, while tuning a parameter h in the contact term can also reproduce the data, and different predictions are presented to distinguish the two schemes by further experimental study. • Analysis of K-p ->p0L data suggest the existence of a new resonance, which is either S(1530)1/2+ or S(1550)1/2-. • Measurements of wider energy range and combined channel analysis will provide more information.

  28. Thank you for your attention！

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