This award funds the research activities of Professor Walter Tangarife at Loyola University Chicago.<br/><br/>Two of the most intriguing puzzles in particle physics are the nature of dark matter and the origin of neutrino masses. Dark matter is a major ingredient of the Universe whose effects on galaxies and other astrophysical objects can be measured by physicists, but no other property of dark matter is yet known. Neutrinos are particles that are described as massless within the so-called "Standard Model of particle physics". However, experiments have shown that while neutrinos are indeed incredibly light, they are not massless. In his research, Professor Tangarife aims to explore testable models in which neutrino physics and the dark-matter problem are intertwined. Research in these topics advances the national interest by promoting the progress of fundamental science through investigation of the laws that govern the universe. This project is also envisioned to have significant broader impacts. Professor Tangarife will involve undergraduate students in his research, providing them with critical skills of great utility in both academic and industrial careers. He also intends to give public lectures on his research results and organize outreach events in high schools within the local community. <br/><br/>More technically, Professor Tangarife will investigate models of keV sterile-neutrino dark matter in the presence of self-interactions. New interactions enhance the production mechanism and provide signals to be probed in next-generation experiments, including DUNE. Additionally, self-interacting sterile neutrinos make good candidates for self-interacting dark matter, which may be relevant for small-structure phenomena. This project will also study Dirac dark-matter models in which the dark matter participates in the generation of masses for the Standard-Model neutrinos. The goal is to constrain scenarios in which the difference between baryon and lepton numbers is a gauge symmetry. The phenomenology of such models will be constrained by dark-matter detection experiments, dark-photon searches, and cosmological bounds.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.