Status Update for the UCN$\tau$ Neutron Lifetime Experiment

The UCN$\tau$ experiment at Los Alamos National Laboratory measures the neutron lifetime by holding ultracold neutrons (UCN) in a magneto-gravitational trap for variable holding times. Precision neutron beta decay measurements provide an important insight into the Standard Model. A combination of measurements of decay correlation coefficients and the neutron lifetime generates an independent, competitive, determination of the CKM matrix element $V_{ud}$. UCN$\tau$ utilizes a permanent magnet array to prevent neutron-wall interactions and thus minimizes non-decay neutron loss mechanisms. During 2017 and 2018, the UCN$\tau$ collaboration gathered enough data to produce a measurement of $\tau_n$ with an expected statistical uncertainty below 0.3s, and an expected systematic uncertainty below +0.2s. We will present the present status of the experiment and analysis, as well as improvements made to achieve UCN$\tau$’s goal of a total uncertainty below 0.25s.