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Coulomb barrier distributions: puzzles and recent experiments Eryk Piasecki and

Coulomb barrier distributions: puzzles and recent experiments Eryk Piasecki and The Barrier Collaboration. September 2006. 58 Ni + 60 Ni. A.M.Stefanini et al., Phys.Rev.Lett. 74(1995)864. Motivation (hopes).

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Coulomb barrier distributions: puzzles and recent experiments Eryk Piasecki and

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  1. Coulomb barrier distributions: puzzles and recent experiments Eryk Piasecki and The Barrier Collaboration September 2006

  2. 58Ni + 60Ni A.M.Stefanini et al., Phys.Rev.Lett. 74(1995)864

  3. Motivation (hopes) • Determination of importance of various couplings (vibrational, rotational, single-particle ones) in different reaction and systems. • What is the influence of the Q of reaction? • What is the influence of formfactors? • Determination of the nuclei deformation parameters (2, 3, 4 and perhaps even 6), including their sign, what is pretty difficult using the standard Coulomb excitation methods. • Reliable calculation of the nucleus-nucleus cross-sections in sub-barrier region. • Optimization of superheavy elements production. • Investigation of the influence of exotic nuclear structures (e.g. “halo”) on the reaction mechanisms.

  4. Two experimental methods:

  5. Are the methods equivalent? H.Timmers et al., NP A 633(1998)421

  6. 16O + 144Sm H.Timmers et al., NP. A584(1995)195

  7. Predictions of Coupled Channels Theory for 20Ne + 118Sn (CCFULL code) Cluster model No couplings Shape of20Ne With couplings b2 = 0.46 b3 = 0.39 b4 = 0.27

  8. What we miss in the calcs??? Suspicion: perhaps the „weak” channels (transfers, s.p. excitations) are not that weak as it is assumed in the CC calculations?

  9. 20Ne + 116Sn p - stripping a - stripping

  10. ~Z1*Z2*b

  11. Estimatedfrom systematics

  12. Estimatedfrom systematics

  13. Expectations & experimental results: 20Ne + 90Zr: weak neutron transfer barrier structure 20Ne + 92Zr: stronger neutron transfer no structure wider barrier distribution

  14. Is the puzzle solved?? • Open questions: • Transfers and/or s.p. exciations? • Quantitative relation between the strength of „weak” channels and barrier smoothing • Why the barrier structure has been observed in many experiments? • Is Dfus as sensitive for smoothing as Dqe? • CC treatment of these problems

  15. Simultaneous measurements of Dfus & Dqe JYU Aug/Sept. 2006

  16. Measurements of weak channels strengths (transfers & s.p. excitations) E MCP START Target beam 20Ne natNi 90,92Zr 118Sn 206,208Pb (E,ToF)  A LToF = 55cm FWHMToF≈ 200ps

  17. SD array Targets MCP

  18. 20Ne + 118Sn 16O 20Ne Time of flight 19Fe 22Ne Energy

  19. Conclusions: • The weak channels can have quite considerable influence on the barrier height distributions • There are still some (interesting) open questions • Transfers and/or s.p. exciations? • Quantitative relation between the strngth of „weak” chanels and barrier smoothing • Why the barrier structure has been observed in many experiments? • Is Dfus as sensitive for smoothing as Dqe? Some of the answers are probably already in our hands and will be presented soon. • CC treatment of these problems is badly needed September 2006

  20. The BARRIERCollaboration: • Warsaw University (Inst. Exp. Phys. & Heavy Ion Lab): • Ł.Świderski, P. & T. Czosnyka, J.Jastrzębski, A.Kordyasz, M.Kowalczyk, M.Kisieliński, K.Piasecki, E.Piasecki • Białystok University:T.Krogulski • Technische Universitat (Darmstadt):M.Mutterer • Radium Institute (St. Petersburg):S.Kchlebnikov, G.Turin • University of Jyvaskyla: W.Trzaska, M. Sillanpää • Tohoku University:K.Hagino • IReS (Strasbourg):N.Rowley • Inst. Nucl. Studies (Warsaw):K.Rusek • LNL (Legnaro):A.Stefanini • LNS (Catania): P.Russotto • JINR (Dubna):E.Kozulin,S.Smirnov • Kurchatov Inst. (Moscow):A.Ogloblin, S.Dmitriev

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