Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

1. RCNP & NuRI + photoproduction with vector K* (including other recent results) Seung-il Nam*1,2 Atsushi Hosaka1 Hyun-Chul Kim2 1.Research Center for Nuclear Physics (RCNP), Osaka Univ., Japan 2.Nuclear physics & Radiation technology Institute (NuRI), Pusan Univ., Korea Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

2. RCNP & NuRI T.Nakano, talk given at Beijing (2005) talk given at Nara (2005) Recent status of Theta • Recent experiments for pentaquark baryons • New evidence for + by LEPS at Spring-8 • (1520) (=*) photoproduction revisited experimentally by LEPS • ++ announced by STAR • No clear evidence for + CLAS at JLAB Negative results from BABAR etc • Controversial experimental situations Considering photoproduction of +, (LEPS and CLAS) Positive results out of neutron target vs. Negative results out of proton target Suppression of total cross section for proton? What is the suppression mechanism? Huang, talk given at Beijing (2005) R.De Vita, talk given at APS (2005) S.Ricciardi [BABAR], hep-ex/0507027 Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

3. RCNP & NuRI Recent status of Theta Theoretical interests in this talk * photoproduction concerning +: new analysis Possible interpretation for CLAS result: Isospin asymmetry + photoproduction with K*: reaction process analysis Theoretical framework Effective Lagrangian approach The Born approximation at tree level Phenomenological form factor maintaining the Ward-Takahashi identity Parameters estimated by phenomenological consideration and model calculation Experimental data used for fixing cutoff  S.I.N et al.,Phys.Rev.D71,114012 S.I.N et al.,hep-ph/0505134, submitted to Phys.Lett.B S.I.N et al.,in preparation Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

4. RCNP & NuRI p  K- D + << 1 *  D + Photoproduction of Lambda* Strong correlation between  and (1520) New evidence of + by LEPS at Spring-8 using deuteron target Simultaneous productions of + and * Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

5. RCNP & NuRI p  * K- D K-p missing mass for  + (1520) invariant mass Photoproduction of Lambda* + photoproduction from deuteron target by LEPS Only for * resonant region, peak for  appears Motivation: Is it possible for extracting information for  via *? Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

6. RCNP & NuRI Photoproduction of Lambda(1520) Photoproduction of (1520) Rarita-Schwinger vector-spinor field W.Rarita et al.,Phys.Rev.60,61 Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Interactions No PS coupling scheme due to = 0 and  = 0 Parameters gKN* =11 (Experiment) gK*N* =0,11 (Quark model)

7. RCNP & NuRI Photoproduction of Lambda*  p  +*: Proton target Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan D.P.Barber [Daresbury],Z.Phys.C7,17 Qulitaively well reproduced experimental data; Cutoff =750 MeV Dominant contact term (Kroll-Ruderman)

8. RCNP & NuRI T.Nakano, talk given at Beijing (2005) talk given at Nara (2005) No K* No K* Photoproduction of Lambda*  n  0*: Neutron target (No data for cross section) Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan ~30 times smaller n than p due to absence of the contact term Large asymmetry actually shown in the recent LEPS experiment

9. RCNP & NuRI Contact K*(spin-1)-exchange K(spin-0)-exchange 3/2 3/2 1/2 1/2 3/2 1/2 Photoproduction of Lambda(1520) K*-dominance scenario proposed by experiments In the experimental analysis, almost (1520) decayed from its |Sz|=3/2 state From this fact, K*-exchange was believed as dominant contribution (t-channel) Theoretical proof: Is this conclusion is correct? D.P.Barber [Daresbury],Z.Phys.C7,17 Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Natural consequences for K and K* Large |Sz|=3/2contribution from the contact term not from K*

10. RCNP & NuRI CLAS high statistics experiment g11 experiment CLAS @JLAB Proton target No obvious peak for  Estimation: p/p< 0.2% Corresponding to p< 2 nb Proton Proton (1520) R.De Vita, talk given at APS (2005) pK0 invariant M nK+ invariant M Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan The cross section from the proton suppressed? Positive evidence from the neutron target (LEPS) Asymmetry between neutron and proton targets? Hinted by (1520) photoproduction If (1520) and + behave similarly in reaction processes: Spin-3/2 +

11. RCNP & NuRI  +  - p (1520) n +(1540) e=1   bar0 0 p n +(1540) (1520) e=0 e=0 e=1 CLAS high statistics experiment Possible explanation for the null results of the CLAS Taking a look at Feynman diagrams… Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan • n-p asymmetry for spin-3/2  photoproduction • Suppression to the proton target!

12. RCNP & NuRI =+1 =-1 Neutron Proton Neutron Proton Photoproduction of Theta(3/2) Photoproduction of +(3/2):Kbar+(3/2) Analogous calculations to * photoproduction: Cutoff =750 MeV Clear n-p asymmetries for two parities  = 1 MeV, g=+1K*N=3gKN and g=-1K*N=1/3gKN (Quark model) p-wave (=+1) and d-wave (=-1) couplings Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

13. RCNP & NuRI } Strong suppression for the proton target Photoproduction of Theta(3/2) Photoproduction of +(3/2): Kbar+(3/2) Clear n-p asymmetry Our estimation with =1 MeV p < 2 nb and n < 30 nb when 3/2+ p < 10 nb and n < 240 nb when 3/2- p< 5 nb and n < 5 nb when 1/2+ Possible explanation for the recent CLAS experiment Experimental data for neutron target is necessary Very2 preliminary CLAS internal report: n < 20 nb Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan N.Baltzell, talk given at CLAS user meeting

14. RCNP & NuRI Photoproduction of Theta(3/2) Photoproduction of +(3/2): K*bar+(3/2) Reaction N    + including N  *bar+subprocess (planned at CLAS) Three vector meson coupling ** necessary for gauge invariance Including (800,0+) withgN = gKN and gK* = gKK*  = 1 MeV, g=+1K*N=3gKN and g=-1K*N=1/3gKN (QM) Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

15. RCNP & NuRI Photoproduction of Theta(3/2) Photoproduction of K*bar+(3/2): Positive parity No obvious n-p asymmetry K-exchange ~ contact term Strong forward scattering Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan d/dt [nb/GeV2] Photon beam asymmetry

16. RCNP & NuRI Photon beam asymmetry Photoproduction of Theta(3/2) Photoproduction of K*bar+(3/2): Negative parity No obvious n-p asymmetry Strong forward scattering Rather different PBA from =+1 Determination of the parity? Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Photon beam asymmetry d/dt [nb/GeV2]

17. RCNP & NuRI 3/2+ 3/2- Photon beam asymmetry Photon beam asymmetry Photoproduction of Theta(1/2) Photoproduction of K*bar+(1/2): Positive parity No obvious n-p asymmetry Strong forward scattering Rather different PBA’s Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan Photon beam asymmetry

18. RCNP & NuRI x z y K*(k2) //K K   N ·pK*  y-z plane Photoproduction of Theta(3/2) Polarizatios in K*bar+ Two polarizations: photon and K* Looking at amplitudes…. Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan When photon perpendicular to scattering plane: K*-contribution disappears

19. RCNP & NuRI Parallel: //K* Perpendicular: K* Photoproduction of Theta(3/2) Polarizatios in K*bar+  //K*: -exchange survives  K*: K-exchange survives } Due to the amplitude structures Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

20. RCNP & NuRI Summary and conclusion (1520) photoproduction Strong correlation between + and * shown by recent LEPS exp. Qualitatively well reproduced data for proton target Predictions for neutron target: much smaller cross sections Dominant contact term contribution: n-p asymmetry or Isospin asymmetry Experiments showed the asymmetry actually Recent CLAS exp. No obvious peak for +: basically proton-photon scattering New LEPS evidence from neutron target: What happened? Strong suppression expected for proton target What is the suppression mechanism? Suggestion: if + spin-3/2, the suppression occurs? Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

21. RCNP & NuRI Summary and conclusion +(3/2) photoproduction Analougous calculations to those of (1520) Obvious n-p asymmetry shown: Suppression to the proton target p < 2 nb and n < 30 nb when 3/2+ ; p < 10 nb and n < 240 nb when 3/2- Less dependent on K*-contribution than spin-1/2 + +(3/2) photoproduction with vector K*bar scalar kaon (800)-exchange possible Two polarizations possible: incident photon and outgoing K* Selection rule for interchanging kaon after fixing photon polarization //K*: -exchange survives ; K*: K-exchange survives Also valid for spin-1/2 baryon photoproduction Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan

22. RCNP & NuRI Thank you very much Workshop on LEPS/SPring-8 new beamline, 28~29 July 2005, RCNP, Japan