Sensitivity of one-neutron knockout to the nuclear structure of halo nuclei

Abstract

Halo nuclei are located far from stability and exhibit a very peculiar structure. Due to their very short lifetime, they are often studied through reactions. Breakup reactions are of particular interest since their cross sections are large for these loosely-bound nuclei. Inclusive measurements of breakup-also called knockout reactions-have even higher statistics. In this proceeding, we study which nuclear-structure information can be inferred from the parallel-momentum distribution of the core of one-neutron halo nuclei after the knockout of its halo neutron. In particular, we analyse the influence of the ground-state wavefunction, the presence of excited states within the halo-nucleus spectrum and resonances in the coreneutron continuum. Our analysis shows that such observables are sensitive to the tail of the ground-state wavefunction. The presence of excited state decreases the breakup strength, and this flux is transferred to the inelastic-scattering channel. This indicates a conservation of the flux within each partial wave. We also show that the parallel-momentum distributions are insensitive to the existence of resonances within the continuum, they can thus be ignored in practice. This independence on the continuum argues that the parallel-momentum distributions are ideal observables to extract very precisely the ANCs of halo nuclei.

Halo effective field theory analysis of one-neutron knockout reactions of Be11 and C15

“…Once coupled with accurate reaction models, these halo-EFT descriptions of 11 Be and 15 C lead to an excellent agreement with breakup and transfer data [27,28,31,32]. The goal of the present study is to see if, following our previous study [23], they can also explain the knockout cross sections measured in Refs. [13,14].…”

“…[28], we assume a nil c-n interaction in the other partial waves, in particular the p ones. First, we do not have any reliable prediction for the corresponding phaseshifts and, second, we know from our previous study that the knockout cross sections are insensitive to the particulars of the c-n continuum [23].…”

“…The uncertainty associated with the choice of this range is negligible, i.e., less than 1.5% for integrated knockout cross sections. We do not include any interaction in the p 3/2 or higher partial waves, first to reproduce the nearly nil phaseshifts predicted ab initio at low 10 Be -n energy [29] and second because the details of the core-neutron interaction in the continuum do not matter in such calculations [23].…”

“…In the case of 15 C, we use an effective potential in the s 1/2 partial wave to reproduce the ground state and go beyond NLO by including an interaction within the d 5/2 wave to describe the bound excited state, that can affect knockout calculations [23]. In this article, we use the parameters of these interactions for a Gaussian range of 1.2 fm, which are given in Table III of Ref.…”

“…In a previous analysis, we have studied the sensitivity of the knockout cross sections of one-neutron halo nuclei to the description of their structure [23]. We have shown that these reactions are peripheral, in the sense that they probe only the tail of the core-halo wave function.…”