K*Λ(1116) Photoproduction and Nucleon resonances

1. BARYONS’2010,7-11 Dec, Osaka, Japan K*Λ(1116) Photoproduction and Nucleon resonances Sang-Ho Kim(金相鎬) (NTG, Inha University, Korea) In collaboration with Hyun-Chul Kim (Inha University), Yong-Seok Oh (Kyungpook National University), Seung-il Nam (Korea Aerospace University)

2. Outline • 1. Introduction & Motivation 2. Theoretical framework ※ Tree-level Born approximation ※ Effective Lagrangian ※ Amplitude and Form factor 3. Numerical results 4. Conclusion 5. Outlook

3. 1. Introduction The meson photoproduction off the nucleon target ◈ It has been a very useful experimental tool to investigate QCD as a hadronic degrees of freedom. ◈ Intheoretical sides, there have been various tools developed to investigate the photoproductions. ◈ Around the world, there are many experimental facilities and collaborations for this purpose, such as the CLAS at JLAB, LEPS at SPring-8, Bonn-ELSA, Tohoku LNS, etc.

4. 1. Motivation L. Guo et al. [CLAS collaboration], hep-ex/0601010 Although the K* production rate is smaller than that for the K, it is still sizable.

5. 1. Motivation Vector strangeness meson, K* photoproduction ◈ It would be a right subject to study the heavy mass hadron productions, according to the recent experimental progesses. ◈ Nucleon resonances in strangeness production will give more information on microscopic hadron studies. ◈ It is interesting to study additional polarization observables together with the photon, target nucleon, and K* polarizations (future works). ◈ Since we do not have much experimental data for this channel, it would be ahighlyprospective subject for the possible future experiments.

6. 2. Theoretical framework ◆ Effective Lagrangians for interaction vertices. ◆ Born approximation at tree level. ◆ Gauge invariant form factor prescription. ◆ Nucleon resonances in a full relativistic way.

7. 2. Born approximation Tree diagrams

8. 2. Effective Lagrangian t-channel K* exchange K exchange κ exchange

9. 2. Effective Lagrangian u-channel and contact term ● This contact diagram is essential to satisfy the gauge-invariance condition.

10. 2. Effective Lagrangian s-channel

11. 2. Amplitude and Form factor Amplitude Form factor common form factor t-channel s-, u-channel

12. 3. Total Cross section γp ―› K*Λ(K*,K,κ,N,Λ,Σ,Σ*) K-meson exchange dominates remarkably. There is considerable discrepancy between the theory and experiment. Therefore, to cure the problem, we are motivated to include the nucleon resonances near the threshold. • there is considerable discrepancy between the theory and • experiment. Therefore, to cure this

13. 3. Total Cross section γp ―› K*Λ(K*,K,κ,N,Λ,Σ,Σ*)

14. 3. Nucleon Resonances ◈ Among thenucleon resonances reported in PDG, we take into account only three- or four-star resonances. ◈ The threshold energy of K*Λ is 2008 MeV. 1) Mass(N*) < 2008 MeV 2) Mass(N*) > 2008 MeV N* = P11(1440, 1/2+)**** N*= G17(2190, 7/2- )**** D13(1520, 3/2 -)**** H19(2220, 9/2+)**** S11(1535, 1/2 - )**** G19(2250, 9/2- )**** S11(1650, 1/2 - )**** I 11(2600,11/2- )*** D15(1675, 5/2 -)**** F15(1680, 5/2+)**** D13(1700, 3/2 -)*** P11(1710, 1/2+)*** P13(1720, 3/2+)**** ? ?

15. 3. Nucleon Resonances 1) Mass(N*) < 2008 MeV ◆ All values of the helicity amplitudes are given experimentally, so thetransition magnetic moments are calculated easily.

16. 3. Nucleon Resonances ◆ The coupling strength of gK*N*Λis unknown. ▶ We treat it as a free parameter, and by varying the value of gK*N*Λ, we can know which nucleon resonance would dominate the process. Assumption : Considering the Nijmegen potential, gK*NΛ= -4.26, kK*NΛ=2.66, we assume that the ratio of gK*N*Λ and kK*N*Λ can be similar, ~1.6.

17. 3. Total Cross section 1. P11(1440,1/2+) 2. P11(1710,1/2+) Spin 1/2+ N* resonances are negligible.

18. 3. Total Cross section 3. S11(1535,1/2-) For |gK*N*Λ| = 7.0~9.0, it’s in a good agreement with the data.

19. 3. Total Cross section 4. S11(1650,1/2-) For |gK*N*Λ| = 5.0~6.0, it’s in a good agreement with the data.

20. 3. Total Cross section 5. D13(1520,3/2-) 6. D13(1700,3/2-) Spin 3/2- N* resonances are relatively small.

21. 3. Total Cross section 7. P13(1720,3/2+) Spin 3/2+ N* resonance is relatively small.

22. 3. Total Cross section 8. F15(1680,5/2+) 9. D15(1675,5/2-) Spin 5/2 N* resonances are negligible.

23. 3. Total Cross section Among the nucleon resonances less than 2008 MeV, P11(1440), P11(1710), D15(1675), and F15(1680) are almost negligible. D13(1520), D13(1700), and P13(1720) contribute slightly. S11(1535) and S11(1650) are most responsible for reproducing the data, when their values of the coupling constants are |gK*N*Λ(1535)| = 7.0~9.0 and |gK*N*Λ(1650)| = 5.0~6.0. |gKN*Λ(1535)| = 1.0~2.0 from the chiral unitary model

24. 3. Nucleon Resonances 2) Mass(N*) > 2008 MeV ◆ The coupling strength of gK*N*Λ is obtained by the SU(6) quark model. ◆ Except for N*(2190), the helicity amplitudes are not known experimentally. Moreover, only the ratio of the N*(2190)’s helicity amplitude is given. ▶ As a trial, we will take into account only G17(2190). Related works are under progress.

25. 4. Conclusion ◈ We investigated the K* photoproduction off the nucleon, γN ―›K*Λ(1116), within the tree level approximation. ◈In addition to K*, K, κ, N, Λ, Σ, Σ* contributions, we consideredmore nucleon resonances to explain the discrepancy between the previous theoretical result and experimental data in the near threshold region. ◈Among them, S11(1535) and S11(1650) are responsible for reproducing the data, when their values for the coupling constant are |gK*N*Λ(1535)| = 7.0~9.0 and |gK*N*Λ(1650)| = 5.0~6.0.

26. 5. Outlook • We will include more higher-spin resonances usingexperimental and theoretical information. 2. Chi-square fitting will be taken into account. 3. Differential cross section, Double polarization observables. 4. Extending present framework into general vector meson-baryon photoproduction.

27. Thank you very much