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Two-component (neutron/proton) statistical description of low-energy heavy-ion reactions

Two-component (neutron/proton) statistical description of low-energy heavy-ion reactions. E. Běták & M. Veselský Institute of Physics, Slovak Academy of Sciences 84511 Bratislava, Slovakia. Introduction Deep-inelastic – effect of neutron/proton composition at periphery

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Two-component (neutron/proton) statistical description of low-energy heavy-ion reactions

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  1. Two-component (neutron/proton)statistical descriptionof low-energy heavy-ion reactions E. Běták & M. Veselský Institute of Physics, Slovak Academy of Sciences 84511 Bratislava, Slovakia EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  2. Introduction • Deep-inelastic – effect of neutron/proton composition at periphery • Time scales of the processes • Possible playground for pre-equilibrium EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  3. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  4. Experiments: 86Kr on 64Ni, 112,124Sn at 25 A MeV: - observed excess of exp. yields of neutron-rich nuclei with Z=32-34 (sometimes in wider range) • explainable within DIT, but better fit with scaled transfer probabilities (for details: Veselský, Souliotis: Nucl. Phys. A765 (2006), 252) EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  5. 86Kr + 64Ni at 25 AMeV Standard DIT ( Tassan-Got & Stefan, NPA 524 (1991) ) Solid - GEMINI, dash-SMM EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  6. Correlation of skin thickness to isovector chemical potential (V. Kolomietz et al, PRC 64(2001)024315, extended Thomas-Fermi calculation) - Rn-Rp determines the difference of N/Z at (Rn+Rp)/2 ( surface ) from the bulk N/Z, correlates to isovector chemical potential - DIT (T-G) : macroscopic formula for Rn-Rp used, values unrealistically large, but bulk N/Z dynamics described well EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  7. Modified DIT (Veselský & Souliotis: Nucl.Phys. A765 (2006)): phenomenological correction, effect of shell structure on nuclear periphery (assuming Rn-Rp vs. n-p correlation) and thus on transfer probabilities estimated as: where S... = S...exp - S...ld ,  is a free parameter ( = 0.53 determined as optimal value), s > 0 fm (only non-overlapping configurations considered) EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  8. 86Kr + 64Ni at 25 AMeV Modified DIT (Veselský & Souliotis: Nucl. Phys. A765) solid - GEMINI, dash -SMM EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  9. DIT Conclusions - 86Kr + 64Ni, 112,124Sn at 25 AMeV - a microscopic correction to macroscopic DIT describes the effect of isospin asymmetry at nuclear periphery - inversion of the bulk isospin flow due to microscopic structure at nuclear periphery - consistent parameters  for all reactions - SMM reproduces the yields of n-rich species well while overestimating the yields of -stable isotopes close to the projectile - GEMINI typically overestimates the width of mass distributions - for p-rich target 112Sn stronger Coulomb interaction supresses the effect of isospin asymmetry at nuclear periphery at s < 1 fm EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  10. Time scale (example): EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  11. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  12. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  13. Pre-equilibrium (exciton model – master eq.): • initial excited zone should follow the Z/N composition of overlapping region – importance of surfaces • initial number of excitons can be estimated from the overlap of nuclei in momentum space at higher energies and at lower energies (below 5 or 10 A MeV above Coulomb) EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  14. Inclusion of spin - HIC: (Běták: Fizika B12 (2003), 11) EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  15. Pre-equilibrium exciton model suitable instrument to describe the effect of the neutron/proton composition of the initial overlapping region. Features: - model estimates of n0 - spin- and energy- distributions of initial phase - spin couplings as necessary - includes also equilibrated (CN) emission EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  16. Thank you EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  17. EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  18. Experiments at fragment separator MARS ( Cyclotron Lab, Texas A&M University ). EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  19. 86Kr + 124Sn at 25 AMeV Standard DIT ( Tassan-Got ) solid - GEMINI, dash -SMM EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  20. 86Kr + 124Sn at 25 AMeV Modified DIT (nucl-th/0507026): solid - GEMINI, dash -SMM EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  21. 86Kr + 112Sn at 25 AMeV Standard DIT ( Tassan-Got ) solid - GEMINI, dash -SMM EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  22. 86Kr + 112Sn at 25 AMeV Modified DIT (nucl-th/0507026): Dash-dotted - SMM, s > 0.8 fm solid - GEMINI, dash -SMM EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  23. 86Kr + 64Ni at 25 AMeV, Exp. vs. Sim. vs Sim. ICF-only EURISOL workshop, ECT* Trento, 16-20 Jan. 2006

  24. M.B. Tsang et al., PRL 86(2001)5023 G. Souliotis et al., PRC 68(2003)24605 Isoscaling in nuclear processes EURISOL workshop, ECT* Trento, 16-20 Jan. 2006 M. Veselský et al., PRC 69(2004)44607

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