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Can we constrain the fusion hindrance?

Can we constrain the fusion hindrance?. David BOILLEY and Hongliang LÜ ( 吕宏亮 ) GANIL and Normandie Université. Yasuhisa ABE ( 阿部恭久 ) RCNP , Osaka : ( 大阪大学核物理研究センター ). Caiwan SHEN ( 沈彩万 ) Huzhou Teachers ’ College : ( 湖州师范学院 ). Anthony Marchix CEA/DSM Saclay.

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Can we constrain the fusion hindrance?

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  1. Can we constrain the fusion hindrance? David BOILLEY and Hongliang LÜ (吕宏亮) GANIL and NormandieUniversité • Yasuhisa ABE (阿部恭久) • RCNP, Osaka: • (大阪大学核物理研究センター) • Caiwan SHEN (沈彩万) • HuzhouTeachers’ College: • (湖州师范学院) Anthony Marchix CEA/DSM Saclay

  2. Reaction to form SHE

  3. Experimental fusion hindrance K.-H. Schmidt & W. Morawek Rep. Prog. Phys.54 (1991) 949

  4. Reseparation Fission Quasi-fission Inner barrier Coulomb barrier SHE Unknown inner barrier

  5. Naik, Loveland et al, Phys. Rev. C 76, 054604

  6. One – two orders of magnitude!

  7. Naik, Loveland et al, Phys. Rev. C 76, 054604

  8. What’s the problem? • The best known part has the same discrepancies than the less known part! • Is it due to uncertainties? Experiments Models

  9. Experimental uncertainties Maximum value of σ1n Z

  10. Survival probability • Bf< Bn=> Fission dominates: • Parameters entering the fission width have a great influence • Fission barrier is most sensitive parameter • Nuisance parameters: • Damping energy: • Friction coefficient:

  11. Nuisance parameters

  12. Fission barriers • In the past: • Nowadays: • Tables: Moller et al

  13. Various models

  14. Various models (2)

  15. Fission barriers (MeV)

  16. Summary

  17. Partial conclusions • Fusion hindrance and fission barriers are both unknown • How to progress? • Measurement of fission barriers: • Heaviest nucleus is No • Microscopic models: • Only the Coulomb barrier

  18. Fusion by diffusion Y. Abe, D. B., B.G. Giraud and T. Wada, Phys. Rev. E61, 1125 (2000) D. B., Y. Abe and JD Bao, Eur. Phys. J. A18, 627 (2003) Effective barrier to have half of the particles to over pass the saddle

  19. Potentiallanscape

  20. Importance of the neck The value of the neck parameterdiffersfromauthors

  21. V()=f.   0 1 Neck dynamics Wesolved the Smoluchowski equation Neck equilibratesveryquickly  <>  0.1

  22. Position of the inner barrier

  23. Fusion hindrance for symmetric reactions

  24. Borderline between hindered and non hindered reactions

  25. Dynamical coupling • Rapid neck evolution affects the initial value of the other parameters: • To the asymmetry parameter: • To the radius: • Initial shift that increases hindrance

  26. Test on a simple case Exact solution for a saddle made with 2 parabolas

  27. Conclusions • Theoretical uncertainty are larger than experimental ones • Uncertainty analysis helps to pin down important parameters • Beyond parameters, reduction to small number of degrees of freedom should be done carefully

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