The puzzle remains in the large discrepancy between neutron lifetime measured by the two distinct experimental approaches—counts of beta decays in a neutron beam and storage of ultracold neutrons in a potential trap, namely, the beam method versus the bottle method. In this paper, we propose a new experiment to measure the neutron lifetime in a cold neutron (CN) beam with a sensitivity goal of 0.1% or sub-1 s. The neutron beta decays will be counted in a superfluid helium-4 scintillation detector at 0.5 K, and the neutron flux will be simultaneously monitored by the helium-3 captures in the same volume. The CN beam must be of wavelength λ > 16.5 Å to eliminate scattering with superfluid helium. A new precise measurement of neutron lifetime with the beam method of unique inherent systematic effects will greatly advance in resolving the puzzle.

中文翻译：

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冷流中子束在超流氦4中的新中子寿命实验

难题仍然在于通过两种不同的实验方法测得的中子寿命之间的巨大差异，即中子束中β衰变的计数和超冷中子在势阱中的存储，即束法与瓶法。在本文中，我们提出了一项新的实验，以测量灵敏度目标为0.1％或1 s以下的冷中子（CN）束中子的寿命。中子β衰变将在0.5 K的超流氦4闪烁探测器中计数，并且中子通量将通过在相同体积中捕获的氦3来同时监视。CN束必须具有λ> 16.5Å的波长，以消除超流氦的散射。用独特的固有系统效应的束方法对中子寿命进行新的精确测量，将在解决难题方面大有进展。