Microscopic description of pair transfer between two superfluid Fermi systems: Combining phase-space averaging and combinatorial techniques

David Regnier, Denis Lacroix, Guillaume Scamps, and Yukio Hashimoto
Phys. Rev. C 97, 034627 – Published 30 March 2018

Abstract

In a mean-field 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 gauge-angles. In the present work, we propose a new approach to obtain the multiple pair transfer probabilities between superfluid systems. This method, called phase-space combinatorial (PSC) technique, relies both on phase-space averaging and combinatorial arguments to infer the full pair transfer probability distribution at the cost of multiple mean-field calculations only. After benchmarking this approach in a schematic model, we apply it to the collision O20+O20 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 O14+O20 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 gauge-angle effects in nuclear reaction and/or for applying the proposed PSC approach on pair transfer is the collisions of identical open-shell spherical nuclei.

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  • Received 27 November 2017

DOI:https://doi.org/10.1103/PhysRevC.97.034627

©2018 American Physical Society

Physics Subject Headings (PhySH)

Nonlinear DynamicsNuclear Physics

Authors & Affiliations

David Regnier* and Denis Lacroix

  • Institut de Physique Nucléaire, IN2P3-CNRS, Université Paris-Sud, Université Paris-Saclay, F-91406 Orsay Cedex, France

Guillaume Scamps and Yukio Hashimoto

  • Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8571, Japan

  • *regnier@ipno.in2p3.fr
  • lacroix@ipno.in2p3.fr

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Issue

Vol. 97, Iss. 3 — March 2018

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