A search for a proposed solution to the neutron lifetime enigma.

The free neutron lifetime measured by two different methods, the decay rate of neutrons in a beam [1] and by the disappearance rate of ultra cold neutron stored in a magnetic bottle[2], disagree by 4.4 standard deviations. A recent proposed solution by Koch and Hummel[3] suggests that a low lying excited state of the neutron can contribute differently to these two experiment and explain the difference in lifetimes. An analysis of data from the UCNτ experiment searching for this effect will be presented.

1. Yue, A., et al., Improved determination of the neutron lifetime. Physical review letters, 2013. 111(22): p. 222501.

2. Gonzalez, F.M., et al., Improved neutron lifetime measurement with ucn τ. Physical review letters, 2021. 127(16): p. 162501.

3. Koch, B. and F. Hummel, An exciting hint towards the solution of the neutron lifetime puzzle? arXiv preprint arXiv:2403.00914, 2024.