The Nab Neutron Decay Correlation Experiment

Neutron decay correlations provide a clean probe of the CKM matrix element $V_{ud}$, and provide limits on new tensor and scalar interactions. The Nab experiment is currently being commissioned at ORNL to measure the antineutrino-electron correlation $a$ with a relative uncertainty of $10^{−3}$, and the Fierz interference term $b$ with an overall uncertainty of $3\times10^{−3}$. This experiment uses a new technique to determine the antineutrino-electron angle from the energy of the electron and proton, detected in coincidence. I will present the physical design, modes of running, and projected sensitivity of this experiment.