Toward an experiment to constrain exotic halo properties from angular differential cross sections of neutron-breakup reactions*

At FRIB, it is now possible to access a greater number of exotic halo nuclei. We plan to perform an experiment to study the neutron halo structure of ¹⁹C with a new technique. The technique proposes to determine the halo properties such as asymptotic normalization coefficients from angular differential cross sections of neutron breakup reactions [1]. Within the technique, the neutron decay energy of the halo nuclei needs to be constrained well by invariant mass spectroscopy. Our experiment therefore involves a complex detector set comprised of the MoNA neutron detector array, the Sweeper Magnet, and the BlueSTEAl Si array [2]. In this work, we have designed our experimental setup with these detectors, developed analysis protocols, and investigated the experiment’s feasibility by Geant4 simulation using the NPTool framework [3]. We simulated neutron breakup reactions from a 45 MeV/u ¹⁹C beam with realistic beam profiles and a ¹²C target.  Each detector was modelled with realistic energy, position, and timing resolution. Configuration of the detector setup was optimized by evaluating the detection efficiency, resolution, background events, and statistics. We conclude that our knowledge of ¹⁹C halo properties can be drastically improved using the currently available detectors and beams at FRIB. These results will be included in our proposal for the FRIB PAC3.