Probing Dark Sectors with Neutron Stars*

Tensions in measurements of neutron and kaon weak decays, such as of the neutron lifetime, may speak to the existence of new particles and dynamics not present in the Standard Model (SM). In scenarios with dark sectors, particles that couple feebly to those of the SM appear. We offer a focused overview of such possibilities and describe how observations of neutron stars, that probe either their structure or dynamics, limit them. In realizing these constraints we highlight how the assessment of particle processes within dense baryonic matter impacts the emerging picture — and we emphasize both the flavor structure of the constraints and their broader connections to cogenesis models of dark matter and baryogenesis.