Dynamical effects in proton breakup from exotic nuclei

TL;DR

This paper investigates the dynamical effects in proton breakup from exotic nuclei, comparing Coulomb and nuclear breakup mechanisms, and identifies key observables for experimental analysis.

Contribution

It provides a comprehensive theoretical treatment of proton breakup, including all Coulomb interactions and multipole expansion, and distinguishes effects of different Coulomb contributions.

Findings

Proton behaves like a more bound neutron due to Coulomb barrier effects.

Direct proton-target Coulomb potential significantly increases breakup cross sections.

Proton angular distributions effectively separate different Coulomb effects.

Abstract

We study dynamical effects in proton breakup from a weakly bound state in an exotic nucleus on a heavy target. The Coulomb interactions between the proton and the core and the proton and the target are treated to all orders, including also the full multipole expansion of the Coulomb potential. The dynamics of proton nuclear and Coulomb breakup is compared to that of an equiva- lent neutron of larger binding energy in order to elucidate the differences with the well understood neutron breakup mechanism. A number of experimentally measurable observables such as parallel momentum distributions, proton angular distributions and total breakup cross sections are calculated. With respect to nuclear breakup it is found that a proton behaves exactly as a neutron of larger binding energy. The extra 'effective energy' is due to the combined core-target Coulomb barrier. In Coulomb breakup we distinguish the effect of the core-target Coulomb potential (called recoil effect), with respect to which the proton behaves again as a more bound neutron, from the direct proton-target Coulomb potential. The latter gives cross sections about an order of magnitude larger than the recoil term. The two effects give rise to complicated interferences in the parallel momentum distributions. They are instead easily separable in the proton angular distributions which are therefore suggested as a very useful observable for future experimental studies.