1. Double-Pionic Fusion in Nucleon Collisions on Few Body Systems - The ABC Effect and its Possible Origin Wasa-at-Cosy Celsius Wasa

2. First step into the ABC Alexander Abashian, Norman E. Booth and Kenneth M. Crowe, Phys. Rev. Lett. 5, 258 (1960) Alexander Abashian, Norman E. Booth and Kenneth M. Crowe, Phys. Rev. Lett. 5, 258 (1960) π 2 π Phase Space inclusive

3. All of ABC No ABC effect! ABC effect

4. ΔΔ ΔΔ Large π π invariant mass Small π π invariant mass π N Δ π N Δ π N Δ π N Δ p n Δ Δ d π π

5. F. Plouin et. al. Nucl. Phys. A302 (1978), 413-422 ABC and ΔΔ models π π π π π π  F. Plouin, P. Fleury, C. Wilkin PRL 65 (1990) 692

6. Results from new exclusive measurements

7. WASA 4  Detector   3 He/d    COSY/

8. What we actually did p n p

9. p d      

10. Total xsection pn  d  +  - pn  d  0  0 Tp = 1.0 GeVTp = 1.2 GeVTp = 1.4 GeV  (  +  0 )=  (I=1)  (  +  - )=0.5  (I=1)+2  (I=0)  (  0  0 )=  (I=0)=0.2  (I=1) pp  d  +  0

11. Total x-section d  threshold  mass

12. 2D x-section

13. Qualitative description n p n Δ Δ d π π + Δ Δ d π π p

14. Total xsection slices: qualitative description

15. M.Bashkanov et. al, Phys. Lett. B637 (2006) 223-228 (I=0,1) (I=0) pd  3 Heππ, T p =0.89 GeV

16. Conclusion ABC effect due to narrow S-channel resonance with ABC effect due to narrow S-channel resonance with – – – ABC resonance: ABC resonance: – eigenstate in isoscalar pn and  systems – robust enough to survive in nuclear medium More than just a  state ? More than just a  state ? –Is it a genuine dibaryon?

17. Outlook Finish data analysis Finish data analysis Perform Partial Wave Analysis (J PC ) Perform Partial Wave Analysis (J PC ) Analysis of Analysis of Measure Measure Measure pn elastic scattering Measure pn elastic scattering

18. Multiplet 10  10=35  28  27  10   *  *+  *  *  +  *  * Y(  )=2 I(  )=0

19.   *  * 

20. Dalitz plot

21. Total xsection slices: qualitative description

22. Parameters of a new state M R = 2.385 GeV  = 53 MeV

23. Total x-section Tp = 1.0 GeV Tp = 1.2 GeV Tp = 1.4 GeV

24. ΔΔ versus Δ pd  3 Heππ, T p =895 MeV

25. ΔΔ ΔΔ π N Δ π N Δ π N Δ π N Δ Large π π invariant mass Small π π invariant mass

26. pn  dππ, T p =1.03 GeV

27. M.Bashkanov et. al, Phys. Lett. B637 (2006) 223-228 (I=0,1) (I=0) pd  3 Heππ, T p =0.89 GeV

28. ΔΔ Resonance p n p n Δ Δ d π π Δ Δ d π π +

29. ΔΔ resonance in differential distributions Δ Δ π π Δ π π Δ Δ π π Δ + Parameter of F(q) is fitted here pd  3 Heππ q ΔΔ  q 

30. ΔΔ resonance parameters

31. Consistent description for d and 3 He case With ΔΔ resonance Without ΔΔ resonance pd  3 He  pn  d  T p =0.895 GeV T p =1.03 GeV T p =1.35 GeV

32. Angular distributions ΔΔ bound ΔΔ peak full pd  3 He  T p =0.895 GeV

33. Angular distributions ΔΔ bound ΔΔ pn  d  T p =1.03 GeV

34. Quantum numbers of the resonance From Fermi-statistics: J=1 +,3 + if L ΔΔ =0 3 S 1   (  d ) : S wave only 3 D 1   (  d ) : S + D waves 3 D 3   (  d ) : no S wave pn  R  d  0  0 1+1+ 3+3+ pn  d  0  0 pn  d  0  0 I=0,1I=0I=0,2 I=0

35. pp  d  +  0  no ABC  * (k 1 x k 2 )  T p =1.1 GeV Control channel (NO ABC expected)

36. Data collected for pn  d  0  0 T p =1.0, 1.1, 1.2, 1.3, 1.4 GeV T p =1.0, 1.1, 1.2, 1.3, 1.4 GeV To cover full resonance region To cover full resonance region To have overlaps between different energies, due to Fermi To have overlaps between different energies, due to Fermi To reduce systematical errors. To reduce systematical errors.

37. Results from dd   +X beamtime Collected energies: T d = 0.8, 0.9, 1.01, 1.05, 1.117, 1.2, 1.25, 1.32, 1.4 GeV

38. Phase shifts pn  pn Elastic scattering

39. Outlook Wasa-at-Cosy Wasa-at-Cosy Nov07-Dec07 dd runs Nov07-Dec07 dd runs Feb08 pd runs Feb08 pd runs

40. ΔΔ - FSI

41. Energy dependence of the low-mass enhancement unbound (ΔΔ) bound ΔΔ 27 MeVbound (ΔΔ) 27 MeV

42. FSI p n p n   p n   n n p n p n p n p p n    d p n     d p n      d p n    +++ + … +++…

43. 3 S 1 phase shifts

44. 3 D 3 phase shifts

45. ΔΔ resonance parameters

46. Effect of collision damping Without collision damping With collision damping

47. Δ resonance π N Δ π N Δ π N Δ L=1

48. Total x-section for ΔΔ resonance ABC channels (I=0) No ABC (I=1)

49. First step into the ABC Alexander Abashian, Norman E. Booth and Kenneth M. Crowe, Phys. Rev. Lett. 5, 258 (1960) Alexander Abashian, Norman E. Booth and Kenneth M. Crowe, Phys. Rev. Lett. 5, 258 (1960) π 2 π Phase Space

50. All of ABC No ABC effect! ABC effect

51. Δ resonance π N Δ π N Δ π N Δ L=1

52. F. Plouin et. al. Nucl. Phys. A302 (1978), 413-422 ABC and ΔΔ models π π π π π π  F. Plouin, P. Fleury, C. Wilkin PRL 65 (1990) 692

53. ΔΔ versus Reality

54. Total x-section for ABC channels (I=0) No ABC (I=1) pp  d  +  0

55. NΔ state in pp  + d  pp

56. Total x-section for ABC channels (I=0) No ABC (I=1) pp  d  +  0