Investigating neutrinos and the weak interaction with Cyclotron Radiation Emission Spectroscopy*

Observations of β decay have long provided a window into the nature of the weak interaction and the particles that participate in it, from prompting Wolfgang Pauli to first propose the neutrino to enabling Chien-Shiung Wu's discovery of parity violation. Today, observation of the β^- spectrum of tritium by the KATRIN collaboration sets the most precise directly measured limit on neutrino mass, while β decay experiments in other nuclei precisely probe the symmetries of the weak interaction. Cyclotron Radiation Emission Spectroscopy (CRES) is an emerging technique that has the potential to surpass the precision of existing methods. The Project 8 Collaboration has set the first CRES-based neutrino-mass limit, demonstrating high resolution and extremely low background. The He6-CRES collaboration has also observed β decay of ¹⁹Ne and ⁶He to search for chirality-flipping interactions. I will introduce CRES, report on both of these recently published results, and describe the outlook for future increases in precision and physics reach.