1. Pion-Nucleon Charge Exchange in the N*(1440) Resonance Region Michael Sadler, Melissa Jerkins and Shon Watson Abilene Christian University For the Crystal Ball Collaboration

2. Crystal Ball Collaboration at BNL A. Barker (deceased), C. Bircher, C. Carter, M. Daugherity, B. Draper, S. Hayden, J. Huddleston, D. Isenhower, M. Jerkins, M. Joy, C. Robinson, M. Sadler and S. Watson, Abilene Christian University, C. Allgower, R. Cadman and H. Spinka, Argonne National Laboratory, J. Comfort, K. Craig* and A. Ramirez*, Arizona State University, T. Kycia (deceased), Brookhaven National Laboratory, M. Clajus, A. Marusic, S. McDonald, B. M. K. Nefkens, N. Phaisangittisakul*, S. Prakhov, J. Price, A. Starostin* and W. B. Tippens, University of California at Los Angeles, J. Peterson, University of Colorado, W. Briscoe, A. Shafi* and I. Strakovsky, George Washington University, H. Staudenmaier, Universität Karlsruhe, D. M. Manley and J. Olmsted*, Kent State University, D. Peaslee, University of Maryland, V. Abaev, V. Bekrenev, N. Kozlenko*, S. Kruglov, A. Kulbardis, and I. Lopatin, Petersburg Nuclear Physics Institute, N. Knecht*, G. Lolos and Z. Papandreou, University of Regina, I. Supek and D. Mekterovic*, Rudjer Boskovic Institute, and D. Grosnick, D. D. Koetke, R. Manweiler and S. Stanislaus, Valparaiso University Experiment Spokespersons * Ph.D. Students (total of 9)

3. Crystal Ball multiphoton spectrometer 672 NaI crystals. Individual PMT’s ~93% of 4π sr

4. V. Bekrenev mounting PM tubes

5. The Crystal Ball

7. Crystal Ball layout in the C6 beam line at the Brookhaven AGS

8. Invariant Mass for neutral meson decay, e.g. π 0 to 2  π 0 rest frame 180° lab frame   

9. Identification of Neutral Mesons from their Invariant Mass πoπo 

10. Non-strange Spectroscopy: π - p  π°n π - p  π°π°n π - p  π°π°π°n π - p  n π - p  n π - p  π°  n Neutron detection Nuclear Physics: π - A  π°X π - A  π°π°X π - A   X Eta decays:  π°   π°π°π°  π°π°  π°π°π°π°  π°π°   π°π°π°   Antiprotons:  neutrals (π°,  Strange Spectroscopy: Quantity of data: 20 momenta for π - p 2 “ π - A 1 “ 8 “ K - p ~310 7  ’s Crystal Ball Data

11. 153 MeV/c

12. 172 MeV/c

13. 185 MeV/c

14. 200 MeV/c

15. 218 MeV/c

16. 247 MeV/c

17. 267 MeV/c

18. 301 MeV/c

19. 320 MeV/c

20. 351 MeV/c

21. 378 MeV/c

22. 408 MeV/c

23. 456 MeV/c

24. 490 MeV/c

25. 532 MeV/c

26. 614 MeV/c

27. 658 MeV/c

28. π - p  π 0 n Overview

29. π - p  π 0 n excitation functions

35. Call for a new determination of the P 11 (1440) resonance parameters  Aliases for the lowest lying state with I = 1/2, J P = 1/2 +  N*(1440)  P 11 (1440)  Roper resonance  First excited state of the nucleon

37. What do we learn from PWA?   Input for  N  term.   Charge symmetry breaking.   Resonance parameters (P 11, S 11, D 13 ) – masses, widths, decay modes.   Interface between experiment and models. Quark models Skyrme models Collective models

38. N(1440) summary in Review of Particle Physics

41. Arndt, et al., Phys. Rev. C69, 035213 (2004).

44. Summary of Pion-Nucleon Reactions and Observables ReactionsObservables π + p  π + pd  /d  π - p  π - pP (=A N ) π - p  π o nA and R π - p   n π - p  π o π o n π - p   n

45. πN Experiments at LAMPF and BNL

46. 625 MeV/c π + p   p    p 625 MeV/c

47. 625 MeV/c π - p   p    p 625 MeV/c

48. 625 MeV/c π - p  π 0 n

49. π - p Total Cross Section 1440

50. P 11 (1440) speed plot from multichannel analysis From D. M. Manley, Proc. of the Workshop on the Physics of Excited Nucleons (NSTAR 2004), World Scientific. Speed = |dT/dW|, where T = elastic T-matrix amplitude.

51. π - p  π 0 π 0 n  tot 1440

52. π - p  π 0 π 0 n Dalitz plots Crystal Ball Prakhov, et al. PRC 69, 045202 (2004)

53. Summary of Present Status   Listings in Review of Particle Properties rely on PWA’s from 1980.   GWU (formerly VPI) analyses fit data well, but not included in averages.   Analyses should include πp->ππN.   PWA for hadronic channels is needed to analyze data from photo- and electro-production of resonances.   No present experimental facilities for baryon spectroscopy (1-3 GeV/c π’s, K’s).

54. Beginnings of a new PWA effort, Abilene 2004

55. Beginnings of a new PWA effort, Zagreb 2005

58. Conclusions  New PWA efforts are needed to determine properties of the P 11 (1440) resonance.  Complete data sets now available.  KH and CMB analyses completed in 1980.  New PWA’s can be extended to higher resonances when data become available from new facilities.  MIPP at FNAL presents a new possibility (if eventually approved) to make measurements in the πN resonance region (1-3 GeV/c) and with kaon beams higher than 3 GeV/c.  J-PARC (near Tokyo) is a future hadron facility. Call for new proposals is expected this year.  An intermediate experiment on non-strange resonances near 1710 MeV is planned at ITEP (Moscow).