1. Two-pion production in Delta-Delta region – approaching the ABC puzzle by exclusive and kinematically complete measurements. T.Skorodko, University Tuebingen for 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  C

3. All of ABC No ABC effect! ABC effect

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

5. π π π π π π  ABC and ΔΔ models

6. M.Bashkanov et. al, Phys. Lett. B637 (2006) 223-228 (I=0,1) (I=0) pd  3 He ππ, T p =895 MeV

7. ΔΔ versus N * decays pd  3 He ππ, T p =895 MeV

8. ΔΔ versus Reality

9. Bound ΔΔ    3 He p d  molecule

10. ΔΔ interaction Migdal-Watson ansatz

11. ABC effect on 3 He and d ΔΔ interaction data of O. Khakimova

12. Total x-section for Celsius/Wasa Heidelberg – Tel-Aviv JINR unbound (ΔΔ) int bound (ΔΔ) int (24 MeV)

13. pp  pp  ABC effect ?  interaction

14. Conclusion It is extremely important to make exclusive measurements: It is extremely important to make exclusive measurements: ABC effect is one bump, not two! ABC effect is one bump, not two! ABC effect may be explained by ΔΔ molecule or by ΔΔ interaction. ABC effect may be explained by ΔΔ molecule or by ΔΔ interaction. Very strong attractive ΔΔ interaction. |a s |  13fm Very strong attractive ΔΔ interaction. |a s |  13fm  tot  indications of ΔΔ bound state.  tot  indications of ΔΔ bound state.