PNNL

Abstract

Project 8 has developed a novel technique, Cyclotron Radiation Emission Spectroscopy (CRES), for direct neutrino mass measurements. This CRES-based experiment on the beta spectrum of tritium has been carried out in a small-volume apparatus. Here we provide a detailed account of the experiment, focusing on systematic effects and analysis techniques. In a Bayesian (frequentist) analysis, we measure the tritium endpoint as 18553+18 -19 (18548+19 -19) eV and set upper limits of 155 (152) eV on the neutrino mass. No background events are observed beyond the endpoint. We also demonstrate an energy resolution of 1.66(19) eV in a resolution-optimized magnetic trap configuration by measuring 83mKr internal-conversion electrons. These measurements establish CRES as a low-background, high-resolution technique with the potential to advance neutrino mass sensitivity.