Magnetic Field Correction in Event Reconstruction for the Project 8 Neutrino Mass Experiment

Project 8 aims to use the novel technique of cyclotron radiation emission spectroscopy (CRES) to measure the atomic tritium beta-decay spectrum endpoint and probe the absolute neutrino mass scale down to 40 meV/c^2. CRES uses an external magnetic field to induce cyclotron motion of beta-decay electrons in order to measure their cyclotron frequency, which is inversely related to the electron energy, thereby allowing the reconstruction of the beta-decay spectrum. To achieve sufficiently long observation times, the electrons are confined by a magnetic trap in the detection region, inducing a periodic axial motion and nullifying the flat background field assumption. Signals from CRES electrons are modulated by the axial trapping frequency, which encodes information about the electrons’ trajectory in the trap. Electrons with different kinematic properties explore different regions of the trap, requiring an event-by-event field correction to reach a target energy resolution of 0.3 eV rms. In this talk, I will cover a strategy for using the cyclotron and axial frequencies of CRES electrons to realize the target energy resolution for Phase III and beyond. The work presented here will serve as the nominal event reconstruction algorithm for data from the Phase III Cavity CRES Apparatus of the Project 8 experiment, with the objective of a world-leading measurement of Kr-83m conversion electron N-lines.

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.