1. Study of few-body problems at WASA Wasa-at-Cosy

2. Content General overview General overview –  decays – dd   0 –  -mesic helium The ABC effect The ABC effect – d  – 

3. See talk A. Winnemoeller Friday 18:40

7. The ABC effect

8. ABC effect Experimentally Experimentally – low-mass enhancement in M – low-mass enhancement in M  – observed in many fusion reactions – accompanied with ΔΔ excitations Theoretically Theoretically –originates from t-channel ΔΔ excitation –expected double-hump structure in M –expected double-hump structure in M  (not supported by experimental observations)

9. pn  d  0  0

10. 2D x-section

11. Total x-section pn  d  +  - pn  d  0  0  (  +  0 )=  (I=1)  (  +  - )=0.5  (I=1)+2  (I=0)  (  0  0 )=  (I=0)=0.2  (I=1) pp  d  +  0 t - channel 

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

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

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

15. Total xsection slices: qualitative description

35. Dalitz plot (peak region)

36. pn  d  0  0 and pp  d  +  0 (p-spectator)(n-spectator)

37.  +  0 invariant mass T p  1GeV pp  2 He     pp  d    

38. ABC in 3 He

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

40. dd  4 He      Invariant Mass     1.117 GeV 0.9 GeV 1.05 GeV See talk A. Pricking Tuesday 17:30

41. Conclusion Conclusion ABC effect due to narrow s -channel resonance with ABC effect due to narrow s -channel resonance with – – – More data next year More data next year –  -decays –dd   0 –dd  (  )  3He+N+ 

42.   *  * 

43. Outlook Finish data analysis Finish data analysis Perform Partial Wave Analysis (J PC ) Perform Partial Wave Analysis (J PC ) –Do we need polarization? Analysis of Analysis of Measure Measure Measure pn elastic scattering Measure pn elastic scattering

44. Multiplet 10  10=35  28  27  10   *  *  Y(  )=2 I(  )=0 Kim Maltman, Nucl. Phys. A501 (1989) 843

45. Data analyzed so far Tp = 1.0 GeV : 70 kEvents(80%) Tp = 1.0 GeV : 70 kEvents(80%) Tp = 1.1 GeV : Tp = 1.1 GeV : Tp = 1.2 GeV : 26 kEvents(15%) Tp = 1.2 GeV : 26 kEvents(15%) Tp = 1.3 GeV : Tp = 1.3 GeV : Tp = 1.4 GeV : 47 kEvents(25%) Tp = 1.4 GeV : 47 kEvents(25%)

46. Angular distribution (in the peak)

47. Dalitz plot

48. Additional corrections and cross-checks

49. Angular distribution (in the peak)

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

52. Corrections for Fermi-motion

53. Cross-checks at pn  d  0  0  0  d  CW: pn  d  000000000000 WaC: pn  d  0  0  0

54. Check of resolution 3  0 PS

55. Resolution In pn  d  0  0  0 the  width  30MeV In pn  d  0  0  0 the  width  30MeV From MC, X-section resolution in pn  d  0  0  30MeV From MC, X-section resolution in pn  d  0  0  30MeV

56. pn  d  0  0 and pp  d  +  0 (p-spectator)(n-spectator)

57. pp  d  +  0 analysis

59.  +  0 invariant mass

60. Total xsection slices: qualitative description

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

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

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

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

65. pn  dππ, T p =1.03 GeV

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

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

68. 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 

69. ΔΔ resonance parameters

70. 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

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

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

73. 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

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

75. 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.

76. 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

77. Phase shifts pn  pn Elastic scattering

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

79. ΔΔ - FSI

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

81. 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    +++ + … +++…

82. 3 S 1 phase shifts

83. 3 D 3 phase shifts

84. ΔΔ resonance parameters

85. Effect of collision damping Without collision damping With collision damping

86. Δ resonance π N Δ π N Δ π N Δ L=1

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

88. 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

89. All of ABC No ABC effect! ABC effect

90. Δ resonance π N Δ π N Δ π N Δ L=1

91. 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

92. ΔΔ versus Reality

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

94. NΔ state in pp  + d  pp

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