Fill and dump measurement of the neutron lifetime using an asymmetric magneto-gravitational trap

Abstract

The past two decades have yielded several new measurements and reanalysis of older measurements of the neutron lifetime. These have led to a 4.4 standard deviation discrepancy between the most precise measurements of the neutron decay rate producing protons in cold neutron beams and the most precise lifetime measured in neutron storage experiments. Measurements using different techniques are important for investigating whether there are unidentified systematic effects in any of the measurements. In this paper we report a new measurement using the Los Alamos asymmetric magnetogravitational trap where the surviving neutrons are counted external to the trap using the fill and dump method. The new measurement gives a free neutron lifetime of stat syst 876.3(2.4) (0.8) n  . Although this measurement is not as precise, it is in statistical agreement with previous results using in situ counting in the same apparatus.