Interplay between valence and core excitation mechanisms in the breakup of halo nuclei

TL;DR

This paper investigates how core and valence excitation mechanisms interact during the breakup of halo nuclei, revealing their interference effects on angular distributions through advanced DWBA calculations and experimental comparison.

Contribution

It introduces a novel extension of the DWBA method that accounts for core excitation effects in both structure and reaction mechanisms of halo nuclei.

Findings

Core excitation significantly influences reaction dynamics.

Interference between mechanisms affects angular distribution patterns.

First clear evidence of core-valence excitation interference in halo breakup.

Abstract

The phenomenon of core excitation in the breakup of a two-body halo nucleus is investigated. We show that this effect plays a significant role in the reaction dynamics and, furthermore, its interference with the valence excitation mechanism has sizable and measurable effects on the breakup angular distributions. These effects have been studied in the resonant breakup of 11Be on a carbon target, populating the resonances at 1.78 MeV (5/2+) and 3.41 MeV (3/2+). The calculations have been performed using a recently extension of the DWBA method, which takes into account the effect of core excitation in both the structure of the halo nucleus and in the reaction mechanism. The calculated angular distributions have been compared with the available data [Fukuda et al., Phys. Rev. C70,054606]. Although each of these resonances is dominated by one of the two considered mechanisms, the angular patterns of these resonances depend in a very delicate way on the interference between them. This is the first clear evidence of this effect but the phenomenon is likely to occur in other similar reactions.