Nuclear Shell Model to the Rescue: Efforts to Resolve a Mystery in Beta Delayed Neutron Emission

Nuclei far from stability can be studied by producing specific short-lived nuclei by beta decay and measuring the subsequent emission of neutrons and gammas. Such experiments are being planned at both Argonne Nat. Lab and at FRIB (Facility for Rare Isotopes, Michigan State University). Meanwhile, some initial experiments found a surprising overabundance of gamma emission. This has broad implications for predictions made in nuclear astrophysics and other applications. It is our goal to understand this overabundance and improve our theoretical description of short-lived nuclei to account for it. To this end, we will discuss our work integrating microscopic calculations of beta decay and other nuclear properties within the shell model framework with a contemporary nuclear reaction model code. We overcome the computational barrier of large shell model dimensions by deploying our newly developed many-body basis truncation method.