Near and sub-barrier reactions of 8B

J J Kolata,Valdir Guimarães,Eli F Aguilera

doi:10.1051/epjconf/201716300031

Abstract

Four classes of measurements that are important for achieving a complete understanding of the reactions of exotic nuclei are identified and classified according to their degree of difficulty. Previously reported data for near- and sub-barrier fusion of 8 B+58 Ni are critically reviewed. The influence of breakup protons on the evaporation proton measurements for this system is shown to be small at all energies except for the lowest one measured, and corrections are made for this process. Model dependencies in the deduced fusion cross sections are assessed using three different evaporation codes. Data sets for targets of 58 Ni and 28 Si are shown to be consistent with each other, and with fusion enhancement up to energies that are greater than the Coulomb barrier Vb (Ec.m. ≲ Vb + 1.5×ћω ). An important difference with the behavior of neutron-halo systems is thereby confirmed. Possible fusion suppression beyond this energy is suggested by the 28 Si data. A proposal to measure the 8 B+40 Ar fusion cross section using an active-target time projection chamber is discussed.

Highlights

The study of nuclear reactions of exotic, weakly-bound nuclei near the limits of stability has revealed a large number of interesting features
The sum of the 58Ni total fusion cross section plus the direct breakup yield equals the experimentally-measured total reaction cross section (Fig. 4). This is similar to the situation for 6He reactions, in which the sum of the fusion and breakup/transfer yields equals the total reaction cross section
In a recent experiment [23] using the prototype activetarget time projection chamber [24] developed at Michigan State University, the fusion cross section for 10Be+40Ar was studied with extremely high efficiency

Summary

Introduction

The study of nuclear reactions of exotic, weakly-bound nuclei near the limits of stability has revealed a large number of interesting features. Most of these studies have been carried out at energies far above the Coulomb barrier, due to the relative unavailability of these beams at Coulomb-barrier energies. Four different types of relevant experiments can be identified and ranked according to their relative degree of difficulty The first of these is elastic scattering, the easiest reaction to study because of its large cross section, which leads to a determination of the total reaction cross section. Another issue addressed by fusion studies of radioactive but not weakly-bound projectiles is the influence of neutron number on the fusion cross section, as for example in Refs. [9, 10] and a work reported at this conference [11]

Elastic scattering and breakup

Fusion

Fusion Studies with a Time Projection Chamber

Modifications to TwinSol

Findings

Summary and Conclusions