From the Detector Characterization to the Analysis of Commissioning Data of the Nab Experiment

Located at the Spallation Neutron Source (SNS) Oak Ridge National Laboratory (ORNL), the Nab experiment aims to test the Standard Model and search for Beyond Standard Model physics through the precision measurement of electron-antineutrino correlation coefficient and Fierz interference term of free neutron beta decay. Kinematics of decay products is reconstructed from measured proton time-of-flight and electron energy, and systematic effects in the energy reconstruction, including Bremsstrahlung energy loss and linearity of the energy calibration, make a sizable addition to the overall systematic uncertainty budget. Using radioactive sources, we have recently performed ex-situ and in-situ characterization of our highly segmented silicon detectors to understand their response functions. The Nab experiment is currently taking commissioning data with silicon detectors installed at both ends of the Nab spectrometer observing neutron decays. I will present, focusing primarily on energy reconstruction, some of the results of our recent detector characterization campaign at ORNL and the commissioning data.