Particle number fluctuations and correlations in transfer reactions obtained using the Balian-Veneroni variational principle
Résumé
The Balian-Veneroni (BV) variational principle, which optimizes the evolution of the state according to the relevant observable in a given variational space, is used at the mean-field level to determine the particle number fluctuations in fragments of many-body systems. For fermions, the numerical evaluation of such fluctuations requires the use of a time-dependent Hartree-Fock (TDHF) code. Proton, neutron and total nucleon number fluctuations in fragments produced in collisions of two $^{40}$Ca nuclei are computed for a large range of angular momenta at a center of mass energy $E_{cm}=128$~MeV, well above the fusion barrier. For deep-inelastic collisions, the fluctuations calculated from the BV variational principle are much larger than standard TDHF results. For the first time, a good reproduction of mass and charge experimental fluctuations is obtained, and the correlations between proton and neutron numbers are determined, within a quantum microscopic approach.
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