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Nuclei at large distance t unneling effects

Neutron transfer reactions at large internuclear distances studied with the PRISMA spectrometer and the AGATA demonstrator. Sub-barrier transfer reactions. Relative role of one- and multi-nucleon transfer channels. Nuclei at large distance t unneling effects.

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Nuclei at large distance t unneling effects

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  1. Neutron transfer reactions at large internuclear distances studied with the PRISMA spectrometer and the AGATA demonstrator

  2. Sub-barrier transfer reactions Relative role of one- and multi-nucleon transfer channels Nuclei at large distance tunneling effects Overlap between transfer and fusion reactions successive direct

  3. Sub-barrier transfer reactions Experimental difficulties Angular distributions are backward peaked in direct kinematics projectile-like particles have low kinetic energy Difficult identification of reaction products in A, Z and Q-values Cross sections are very small (need for high efficiency)

  4. Reaction in inverse kinematics with PRISMA beam direction PRISMA 20o 96Zr 40Ca Prisma acceptance

  5. The PRISMA magnetic spectrometer Laboratori Nazionali di Legnaro – INFN (Italy) g-array PRISMA

  6. The PRISMA magnetic spectrometer D. Montanari et al., Eur. Phys. J. A (2011) 47 D. Montanari et al., Phys. Rev. C 84, 054613 (2011) S. Szilner et al, Phys. Rev. C 76, 024604 (2007) • Detectors: • entrance detector (MCP) • focal plane detector (MWPPAC) • ionization chamber (IC) • Optics: • quadrupole magnet • dipole magnet

  7. Sub-barrier transfer reactions Neglecting correlations (successive transfer): P(2) = P(1)*P(1) P(3) = P(1)*P(1)*P(1) Enhancement needed for two particle transfer probabilities R. Künkel et al., Z. Phys. 336(1990)336

  8. Previous experiment - 96Zr+40Ca slopes in nice agreement with those expected from the binding energies P1n P4n ~ (P2n)2 P3n ~ P2n P1n P2n ~ 3 (P1n)2 L. Corradi, FUSION11, St. Malo – France

  9. Previous experiment - 96Zr+40Ca Experiment vs microscopic calculation +1n well reproduced by theory in slope and absolute value Same slope of +2n between theory and experiment +2n enhancement due to the presence of other excited states? Absorption reproduced by theory L. Corradi et al., Phys. Rev. C 84, 034603 (2011)

  10. The experiment – 60Ni +116Sn Ground state Q-values Closed-shell Superfluid

  11. The experiment – 60Ni +116Sn PRISMA + AGATA PRISMA only Direct kinematics Inverse kinematics Angular distributions qlab = 50° and 70° (D ≈ 14.5 fm and 16.7 fm) Excitation function Ebeam = 410 – 500 MeV (qlab = 20°) (D ≈ 12.3 to 15.0 fm) Gamma-rays used to estimate the population of excited states Ground state Q-values Closed-shell Superfluid

  12. A/q [a.u.] The experiment – 60Ni +116Sn PRISMA + AGATA PRISMA only Direct kinematics Inverse kinematics Angular distributions qlab = 50° and 70° (D ≈ 14.5 fm and 16.7 fm) Excitation function Ebeam = 410 – 500 MeV (qlab = 20°) (D ≈ 12.3 to 15.0 fm) RV [a. u.] X-ppac [a.u.] Energy [a.u.]

  13. The experiment – 60Ni +116Sn Qvalues for 96Zr+ 40Ca Qvalues for 116Sn + 60Ni

  14. The experiment – 116Sn + 60Ni Slopes for 116Sn + 60Ni Preliminary data Data under analysis +1n and +2n slopes are in agreement with those expected from binding energies PRELIMINARY

  15. Conclusions • We performed sub-barrier transfer reactions in direct and inverse kinematics for a superfluid system (previously with closed-shell system) • Possibility offered by the g-array to estimate the population of excited states in reaction products • Analysis for both direct and inverse kinematics is in progress Next steps • Future goals • - More systematics, e.g. nuclei of different structure • Studying n-p correlations • [experiment proposed and approved at the LNL – INFN (Italy)]

  16. The end

  17. Probing nucleon-nucleon correlations via transfer of (nn), (pp) and (np) pairs at sub-barrier energies in 92Mo+54Fe PRISMA Grazing code calculations S.Szilner, L.Corradi, G.Pollarolo et al, May 2012 LNL PAC Proposal (approved)

  18. Two particle transfer (semiclassical theory, microscopic calculations) 3 terms : simultaneous, orthogonal and successive only the successive term contributes to the transfer amplitude

  19. One particle transfer (semiclassical theory) to obtain the total transfer probability we summed over all possible transitions that can be constructed from the single particle states in projectile and target the set of single particle states covers a full shell below the Fermi level for 96Zr and a full shell above for 40Ca

  20. Magnetic spectrometers for transfer reaction studies 70’s 80’s - 90’s recent years Light ions (Q3D) Heavy ions spectrometers Tracking spectrometers single particle levels (shell model) nucleon-nucleon correlations (pair transfer) A,Z yields cross sections Q-value distributions Reaction mechanism Gamma spectroscopy 3-5 msr 5-10 msr 80-100 msr

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