Microscopic description of pair transfer between two superfluid Fermi systems: Combining phasespace averaging and combinatorial techniques
Abstract
In a meanfield description of superfluidity, particle number and gauge angle are treated as quasiclassical conjugated variables. This level of description was recently used to describe nuclear reactions around the Coulomb barrier. Important effects of the relative gauge angle between two identical superfluid nuclei (symmetric collisions) on transfer probabilities and fusion barrier have been uncovered. A theory making contact with experiments should at least average over different initial relative gaugeangles. In the present work, we propose a new approach to obtain the multiple pair transfer probabilities between superfluid systems. This method, called phasespace combinatorial (PSC) technique, relies both on phasespace averaging and combinatorial arguments to infer the full pair transfer probability distribution at the cost of multiple meanfield calculations only. After benchmarking this approach in a schematic model, we apply it to the collision ^{20}O+^{20}O at various energies below the Coulomb barrier. The predictions for one pair transfer are similar to results obtained with an approximated projection method, whereas significant differences are found for two pairs transfer. Finally, we investigated the applicability of the PSC method to the contact between nonidentical superfluid systems. A generalization of the method is proposed and applied to the schematic model showing that the pair transfer probabilities are reasonably reproduced. The applicability of the PSC method to asymmetric nuclear collisions is investigated for the ^{14}O+^{20}O collision and it turns out that unrealistically small single and multiple pair transfer probabilities are obtained. This is explained by the fact that relative gauge angle play in this case a minor role in the particle transfer process compared to other mechanisms, such as equilibration of the charge/mass ratio. We conclude that the best ground for probing gaugeangle effects in nuclear reaction and/or for applying the proposed PSC approach on pair transfer is the collisions of identical openshell spherical nuclei.
 Publication:

Physical Review C
 Pub Date:
 March 2018
 DOI:
 10.1103/PhysRevC.97.034627
 arXiv:
 arXiv:1711.09812
 Bibcode:
 2018PhRvC..97c4627R
 Keywords:

 Nuclear Theory;
 Condensed Matter  Superconductivity
 EPrint:
 Phys. Rev. C 97, 034627 (2018)