Measuring the Neutron Lifetime with UCNτ+

A free neutron provides the simplest example of nuclear β-decay, leading to a unique suite of tests for fundamental parameters of electroweak theory. The neutron lifetime τ_n, in conjunction with other neutron β-decay observables, can be used to extract V<span style="font-size:10.8333px">ud experimentally. The UCNτ experiment at Los Alamos National Laboratory (LANL) traps ultracold neutrons (UCN) in a magnetogravitational “bottle” for periods of time longer than the neutron lifetime. A permanent magnet Halbach array minimizes neutron losses, ensuring that the loss rates of neutrons in UCNτ generate systematic corrections no greater than the statistical precision of the experiment. UCNτ is the world’s most precise neutron lifetime experiment, allowing it to directly probe recent developments in β-decay theory. Subsequent work, as part of the UCNτ+ experiment, takes advantage of the same measurement technique but with higher statistical reach. We will discuss the most recent UCNτ results and the path towards an even better measurement of the neutron lifetime.