1. 16 March 2009 EuNPC, Bochum 0 Kaon Photoproduction Results from CLAS D. G. Ireland

2. 1 “Missing” Baryon Resonances

3. 2 Resonance Hunting… Mostly done with  N scattering or photoproduction Missing resonances may decay through other channels Total Cross-sections + differential cross-sections + Partial Wave Analysis +... 0.5 1.0 1.5 Cross section E  (GeV )   P 33 N(1440)P 11 N(1520)D 13 N(1535)S 11  (1600)P 33

4. 3 Meson Photoproduction Cross Sections

5. 4 Evidence for new resonance? With D 13 Without D 13 Mart & Benhold, Phys. Rev. C 61 012201(R) (1999)

6. 5 Transversity Amplitudes b 1 = 1 / 2 [(S 1 + S 2 ) + i(N - D)] } } } } b 2 = 1 / 2 [(S 1 + S 2 ) - i(N - D)] b 3 = 1 / 2 [(S 1 - S 2 ) - i(N + D)] b 4 = 1 / 2 [(S 1 - S 2 ) + i(N + D)] N, S 1,S 2, D: Helicity Amplitudes

7. 6 Experimental Observables

8. 7  p →K  Reaction Kinematics proton K+K+ Cross Section without target polarisation Hyperon is self-analysing

9. 8 CEBAF at Jefferson Laboratory

10. 9 CLAS

11. 10 Tagged Photons at CLAS E  = E 0 – E’ Circular Polarisation: polarised electron beam, amorphous radiator Linear polarisation: Crystal (diamond) radiator

12. 11  p →K  Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

13. 12 Recoil Polarisation proton K+K+ Hyperon is self-analysing

14. 13 Recoil Polarisation (P)  p→K  Guidal, Laget, Vanderhaeghen GENT Kaon-MAID J. McNabb et al. (CLAS) Phys. Rev. C 69, 042201 (2004).

15. 14 Beam-Recoil Double Polarisation (C x’,C z’ ) proton K+K+ Hyperon is self-analysing

16. 15  Polarisation →  fully polarised R. Bradford et al., Phys. Rev. C 75, 035205 (2007).

17. 16 Photon Beam Asymmetry (  ) proton K+K+

18. 17 Linear Polarisation analysis   Photon Linear Polarisation Particle ID Thesis work of Craig Paterson (Glasgow)

19. 18  p →K  Photon Beam Asymmetry

20. 19  p →K  Photon Beam Asymmetry PRELIMINARY

21. 20  p →K  Photon Beam Asymmetry PRELIMINARY

22. 21 Beam-Recoil Double Polarisation (  x,O z ) proton K+K+

23. 22  p →K  Extracting O x and O z

24. 23  p →K  Beam-Recoil O x and O z O x PRELIMINARY O z PRELIMINARY

25. 24 Experimental Observables

26. 25 Outlook – Deuterium Target Data taking completed Currently being analysed Data on quasifree neutron and proton Circular and Linear Polarisation

27. 26 Outlook – FROzen Spin Target (FROST) Target can be longitudinally or transversely polarised “Complete” measurement possible First part of run complete Undergoing calibration Second period to run soon…

28. 27 Conclusions Kaon Photoproduction results from CLAS: Published results: , P, C x, C z Preliminary results: , T, O x, O z In the near future: Same set of results for 2 H target (quasifree neutron and proton) “Complete” results (FROST) Next few years: Complete set on 2 H and p (HDIce)

29. 28 Backup Slides…

30. 29 Resonances in Quark Models

31. 30 Kaon Photoproduction

32. 31 Contributing Processes + channel coupling…

33. 32 Helicity Amplitudes N No overall helicity flip = |  –  p  | } S 1 Single helicity flip } S 2 Single helicity flip } D Double helicity flip }

34. 33 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

35. 34 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

36. 35 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

37. 36 Beam-Recoil Double Polarisation C z R. Bradford et al., Phys. Rev. C 75, 035205 (2007). Saclay, Argonne, Pittsburgh Bonn, Giessen, Gatchina Kaon-MAID Regge+Resonance GENT Shklyar Lenske Mosel

38. 37 Beam-Recoil Double Polarisation C xGENT Saclay, Argonne, Pittsburgh Bonn, Giessen, Gatchina Kaon-MAID Regge+Resonance Shklyar Lenske Mosel R. Bradford et al., Phys. Rev. C 75, 035205 (2007).

39. 38 Photon Beam Asymmetry

40. 39 Photon Beam Asymmetry PRELIMINARY

41. 40 Photon Beam Asymmetry PRELIMINARY

42. 41 Recoil - Comparison g8b Prev CLAS GRAAL ~Factor of 4 increase in statistics from best previous measurements PRELIMINARY