An adiabatic hyperspherical treatment of halo nuclei in the few body sector

An area of the few body sector that provides a natural class of systems near the unitarity limit is low-energy nuclear physics. These systems include halo nuclei, which are good candidate systems to study the near-unitarity limit and universality. Two–neutron halos have been extensively studied, such as ⁶He, ⁹B,¹¹Li, ¹²Be, and ¹²C. With the large neutron-neutron (nn) ¹S₀ scattering length (a_s≅-18.5 fm), halo nuclei are good candidates to study universal physics near the unitarity limit and the possible emergence of Efimov physics in Borromean systems or the scattering continuum. In this work, we use the adiabatic hyperspherical representation to study halo nuclei consisting of four neutrons. The adiabatic hyperspherical representation has been extensively applied to few-body systems, in which a description of all possible reaction pathways is treated on an equal footing from treating a collective coordinate, the hyperradius, adiabatically. This work focuses on the ⁴He+4n system, which has been of recent theoretical interest sparked by the 2022 experiment by Duer et. al. that found a low-energy 4n signal in the missing mass spectrum of the ⁸He(p,p⁴He)4n reaction. This work aims to provide theoretical insight into the qualitative and quantitative nature of the five-body scattering continuum and possible universal physics arising in four-neutron halos from the nn interaction.