Examining empirical evidence of the effect of superfluidity on the fusion barrier

TL;DR

This study empirically investigates how superfluidity influences the fusion barrier width, confirming that superfluid systems exhibit larger barrier fluctuations, primarily due to superfluidity and deformation effects.

Contribution

It introduces a new integral method for accurately determining barrier fluctuations and provides empirical evidence of superfluidity's effect on fusion barrier width.

Findings

Superfluid systems show larger barrier fluctuations than magic nuclei.

Superfluidity enhances the fusion barrier width by about 1 MeV.

The new integral method improves fluctuation measurement accuracy.

Abstract

Background: Several Time-Dependent Hartree-Fock-Bogoliubov (TDHFB) calculations predict that the super- fluidity enhances the fluctuations of the fusion barrier. This effect is not fully understood and not yet revealed experimentally. Purpose: The goal of this study is to investigate empirically the effect of the superfluidity on the fusion barrier width. Method: First, the local regression method is introduce and used to determine the barrier distribution more precisely. A second method that requires only the calculation of an integral of the cross section is developed to determine accurately the fluctuations of the barrier. A benchmark is done between this two methods and with the fitting method usually used. This integral method showing a better agreement in a test case, it is applied systematically in a selection of 115 fusion reactions. Results: The fluctuations of the barrier for superfluid systems are on average larger than for magic or semi-magic nuclei. This is due to the deformation effects and the effect of the superfluidity. To disentangle those two effects, we compare the experimental width to the width estimated from a model that takes into account the tunneling, the deformation and the vibration effect. The deviation of the experimental width from this theory for reaction between superfluid nuclei shows that the superfluidity enhance the fusion barrier width. Conclusions: This analysis shows that the predicted effect of the superfluidity on the width of the barrier is real and is of the order of 1 MeV.