Overview and Current Status of the Nab Experiment

The Nab Experiment is designed to make a precise measurement of two correlation parameters in free neutron beta decay: "a", the electron-neutrino angular correlation parameter, and "b", the Fierz interference term. A high-precision determination of "a", when combined with measurements of the neutron lifetime, enables a test of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, a fundamental prediction of the Standard Model. The Nab Experiment is currently taking data at the Spallation Neutron Source at Oak Ridge National Laboratory using a seven-meter-tall, cryogen-free superconducting magnetic spectrometer. Neutrons decay within a decay volume inside the spectrometer, and the resulting electrons and protons are guided by the magnetic field onto silicon detectors located at both ends of the spectrometer. By reconstructing the electron energy and proton time-of-flight, Nab maps out the kinematics of neutron beta decay and allows for the extraction of correlation parameters with high sensitivity. This talk will present an overview of the Nab apparatus, summarize the current status of data-taking and analysis efforts, and outline the path toward delivering the most precise determination of the correlation parameter "a".