Nab Detector In-situ Timing Study*

The neutron beta decay process provides us with sensitive means to probe the weak nuclear interaction for potential new physics beyond the standard model. The Nab experiment will take high precision measurements of the electron-neutrino correlation parameter, a, and the Fierz interference term, b, by precisely measuring the two observables, proton time of flight, and electron energy. The proton momentum is extracted from the proton time of flight. The systematic error budget for Nab demands the average proton time of flight should be known with an uncertainty less than 1 ns. To characterize the timing of the Nab detectors, we will perform a high precision in situ measurement of the Nab Si detectors. This entails using a NaI gamma detector and high quality digitizer as a coincidence tag for the Si detectors with radioactive sources. This will allow us to evaluate the timing systemic effects of the Nab experiment. This poster will focus on the characterization of the NaI detectors as well as the coincidence method for in situ measurements.