Tritium endpoint measurement and neutrino mass limit of Project 8 Phase II

Project 8 is a neutrino mass experiment that uses a new technique, Cyclotron Radiation Emission Spectroscopy (CRES), to make a differential measurement of the tritium β− spectrum. Project 8 aims to use the advantages of CRES to surmount the systematic and statistical limitations of current-generation direct neutrino mass measurement methods, proceeding in a phased approach toward a goal of effective electron antineutrino mass sensitivity of ∼40 meV/c2 using atomic tritium. We report on the results of Project 8's Phase II using molecular tritium: the tritium endpoint measurement and neutrino mass limit, as well as a demonstration of low background. Using 83mKr data, we highlight the excellent energy resolution of CRES, our improved understanding of the detector response, and their impact on the tritium analysis results.

This work is supported by the US DOE Office of Nuclear Physics, the US NSF, the PRISMA+ Cluster of Excellence at the University of Mainz, and internal investments at all institutions.