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

## TL;DR

This study investigates how the structure of halo nuclei influences one-neutron knockout reactions, demonstrating that the parallel-momentum distribution of the core is sensitive mainly to the wavefunction's tail, making it a reliable probe for nuclear structure analysis.

## Contribution

The paper provides a detailed analysis of the sensitivity of knockout observables to halo nuclear structure using an eikonal model and effective field theory descriptions, highlighting the robustness of the parallel-momentum distribution as a probe.

## Key findings

- The knockout reaction is purely peripheral, sensitive only to the wavefunction's asymptotics.
- Presence of excited states reduces breakup cross section amplitude.
- Resonances in the continuum do not affect the parallel-momentum distribution.

## Abstract

Background: Information about the structure of halo nuclei are often inferred from one-neutron knockout reactions. Typically the parallel-momentum distribution of the remaining core is measured after a high-energy collision of the exotic projectile with a light target. Purpose: We study how the structure of halo nuclei affects knockout observables considering an eikonal model of reaction. Method: To evaluate the sensitivity of both the diffractive and stripping parallel-momentum distributions to the structure of halo nuclei, we consider several descriptions of the projectile within a halo effective field theory. We consider the case of 11Be, the archetypical one-neutron halo nucleus, impinging on 12C at 68 MeV/nucleon, which are usual experimental conditions for such measurements. The low-energy constants of the description of 11Be are fitted to experimental data as well as to predictions of an ab initio nuclear-structure model. Results: One-neutron knockout reaction is confirmed to be purely peripheral, the parallel-momentum distribution of the remaining core is only sensitive to the asymptotics of the ground-state wavefunction and not to its norm. The presence of an excited state in the projectile spectrum reduces the amplitude of the breakup cross section; the corresponding probability flux is transferred to the inelastic-scattering channel. Although the presence of a resonance in the core-neutron continuum significantly affects the energy distribution, it has no impact on the parallel-momentum distribution. Conclusions: One-neutron knockout cross section can be used to infer information about the tail of the ground-state wavefunction, viz. its asymptotic normalization coefficient (ANC). The independence of the parallel-momentum distribution on the continuum description makes the extraction of the ANC from this observable very reliable.