Evidence for the Be 15 ground state from Be 12 + 3 n events

Le résumé fourni par la source

Background: $^{15}\mathrm{Be}$ is an unbound nuclide that has been observed to decay by one-neutron emission. Shell model calculations predict two low-lying states in its energy spectrum; however, only a single resonance has been observed from coincident measurements of $^{14}\mathrm{Be}+n$. It has been suggested that the yet unobserved state may decay sequentially through the first excited state in $^{14}\mathrm{Be}$ followed by a two-neutron emission to $^{12}\mathrm{Be}$.Purpose: The ground state of $^{15}\mathrm{Be}$ has yet to be confirmed. A search for this predicted $^{15}\mathrm{Be}$ state by reconstructing $^{12}\mathrm{Be}+3n$ events allows a possible determination of its ground state properties.Methods: A neutron-pickup reaction was performed with a $^{14}\mathrm{Be}$ beam on a ${\mathrm{CD}}_{2}$ target (where D denotes ${}^{2}\mathrm{H}$) to populate unbound $^{15}\mathrm{Be}$ states. Decay energies were reconstructed using invariant mass spectroscopy by detecting $^{12}\mathrm{Be}$ daughter nuclei in coincidence with up to three neutrons.Results: Evidence for at least one resonance in $^{15}\mathrm{Be}$ is presented based on the reconstruction of $^{12}\mathrm{Be}+3n$ events. Through comparison with simulations, the energy of the strongest resonance in the analyzed reaction and decay channel is determined to be ${E}_{{12}_{\mathrm{Be}}+3n}=330(20)\phantom{\rule{4pt}{0ex}}\mathrm{keV}$.Conclusions: The inclusion of a new $^{15}\mathrm{Be}$ state among the $^{12}\mathrm{Be}+3n$ events lower in relative decay energy than the previous $^{14}\mathrm{Be}+\mathrm{n}$ observations provides the best fit to the data. Because this suggested new state would be lower in energy than the previously observed state, it is a candidate for the ground state of $^{15}\mathrm{Be}$.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.