A next generation neutron lifetime experiment based on UCNτ*

The UCNτ experiment measures the free neutron lifetime by in situ counting of surviving ultracold neutrons after different storage times in an asymmetric magneto-gravitational storage volume.  This experiment has acquired sufficient data for a measurement of the neutron lifetime with a statistical uncertainty of about 0.35 s and has demonstrated a systematic uncertainty of 0.28 s [1]; it is expected to ultimately reach a total uncertainty of about 0.2 s.  To achieve even better precision in follow-on experiments, at the 0.1 s level and beyond, the leading sources of uncertainty, including counting statistics, vibrational heating of the stored neutrons, evolution of the stored neutron population in phase space, rate-dependent counting efficiency effects, and depolarization of stored neutrons, must be addressed.  In this talk, we will discuss strategies for how to reduce these sources of uncertainty to achieve a total uncertainty on the neutron lifetime well below 0.1 s in future experiments based on the UCNτ concept, including increasing the storage volume, the strength of the confining magnetic field, or both.

[1] R. W. Pattie Jr. et al., Science 10.1126/science.aan8895 (2018).