Grant: Subatomic Physics Envelope - Individual

Clues to the astrophysical origins of the heaviest elements observed in nature can be identified in a multitude of observables. For instance, our Sun reveals that the conditions in which it was born contained traces of elements synthesized by the slow (s) and rapid (r) neutron capture processes, which are responsible for the heaviest elements observed in nature. These processes have fingerprints in the form of distinct "peaks" seen in solar and stellar elemental abundances. Computational methods provide a modern way to go backwards from observables to fundamental physics. The proposed work will train a machine learning algorithm to recognize r-process and s-process patterns. Then when confronted with stellar patterns, it can provide an estimate of the contributions of each process. Previously we applied statistical methods to find the nuclear mass required to form the solar r-process rare-earth peak (containing elements such as europium) which is presently of uncertain origin. Comparisons between our predicted masses and those measured in laboratories provided insights on the astrophysical production of rare-earth elements. Proposed work will expand upon this by considering alternative statistical methods and by targeting masses of nuclei known to be responsible for other solar abundance peaks. Access to additional observables has grown in recent years, evidenced by multi-messenger detections such as the first ever observed binary neutron star merger (NSM) GW170817, from which both the gravitational wave and light was detected. The light from this event provided the first direct evidence that NSMs synthesize at least some r-process elements. However, whether NSM events produce the heaviest species such as gold and uranium, and whether mergers explain the heavy element content of our Solar System, remains unclear. Proposed work will build on previous studies which compared the NSM frequency inferred from GW170817 to the predicted frequency needed to explain europium in the Solar System by examining other elements and incorporating future detections. Proposed work will also build a catalog of light curve predictions when specific isotopes are produced to help identify the presence of species in future NSMs. Since our ability to interpret observables is critically influenced by the nuclear properties of species both within and beyond experimental reach, these studies will serve to guide future theoretical and experimental research programs. Hydrodynamic simulations are refining our understanding of explosive events such NSMs and exotic magneto-rotationally driven supernovae (MHDs) which could host an r process. Since neutrino interactions critically influence the predicted nucleosynthesis, proposed work will include a first treatment of the magnetic interaction of neutrinos in MHDs. The proposed studies will therefore synergize simultaneous progress across disciplines to address the fundamental open science question of our own cosmic origins.