On nucleon exchange mechanism in heavy-ion collisions at near-barrier energies

TL;DR

This paper investigates nucleon transfer mechanisms in heavy-ion collisions near the Coulomb barrier using a stochastic mean-field approach, comparing results with quantum calculations and emphasizing the role of window motion.

Contribution

It introduces a semiclassical stochastic mean-field framework for nucleon transfer, aligning diffusion and drift coefficients with phenomenological models and comparing with TDHF results.

Findings

Variance of mass distribution matches empirical formula

Drift coefficient underestimates quantum results below barrier

Window motion significantly influences nucleon transfer

Abstract

Nucleon drift and diffusion mechanisms in central collisions of asymmetric heavy-ions at near-barrier energies are investigated in the framework of a stochastic mean-field approach. Expressions for diffusion and drift coefficients for nucleon transfer deduced from the stochastic mean-field approach in the semiclassical approximation have similar forms familiar from the phenomenological nucleon exchange model. The variance of fragment mass distribution agrees with the empirical formula $\sigma^2_{AA}(t)= N_{\rm exc}(t)$. The comparison with the time-dependent Hartree-Fock calculations shows that, below barrier energies, the drift coefficient in the semiclassical approximation underestimates the mean number of nucleon transfer obtained in the quantal framework. Motion of the window in the dinuclear system has a significant effect on the nucleon transfer in asymmetric collisions.