Search for ¹⁵Be decays to ¹²Be+3n

¹⁵Be is an unbound nuclide that has been observed to decay by the emission of a single neutron to the ground state of ¹⁴Be. The ground state of ¹⁵Be could not be confirmed because of a possible decay at lower energy through an unbound state in ¹⁴Be which would emit two more neutrons. The present work is an attempt to search for these decays consisting of ¹²Be and three neutrons originating from unbound states in ¹⁵Be populated via a neutron transfer from a CD₂ target to a ¹⁴Be beam. This experiment was performed at the National Superconducting Cyclotron Laboratory using the Modular Neutron Array (MoNA) and Sweeper magnet setup to detect the neutrons and charged particles, respectively, from the decays. Using invariant mass spectroscopy, the two-, three-, and four-body decay energies were reconstructed. The data were interpreted by comparing the experimental decay energies to those produced by detailed Monte Carlo simulations. Preliminary results indicate the observation of an unbound state in ¹⁵Be constructed from ¹²Be+3n at a comparable energy to the previously observed state that decays to ¹⁴Be+n.