New measurement of the neutron lifetime with a large gravitational trap

The lifetime of the neutron is one of the key physical quantities used to determine the weak interaction parameters and to test predictions of the theory of primary nucleosynthesis. The lifetime of the neutron has been measured in the reported experiment by the method of storing neutrons in a material trap with a gravitational valve. Fomblin grease UT-18 hydrogen-free fluorine polymer has been used as coating. The resistance of the coating to repeated cooling down to $80$ K combined with heating up to $300$ K has been studied. The probability of losses in the trap is as small as $1.5\%$ of the neutron decay probability. The lifetime of the neutron $\tau_{\text{n}}=(881.5\pm0.7_{\text{stat}}\pm0.6_{\text{syst}})$s obtained at the new step is in good agreement with a commonly accepted value of $(880.2\pm1.0)$s presented by the Particle Data Group.