Neutron lifetime experiments using magnetically trapped neutrons: optimal background correction strategies

In the first stage of each run of a neutron lifetime experiment, a magnetic trap is filled with neutrons. In the second stage of each run, decay event s plus background events are observed. In a separate experiment, background is measured. The mean lifetime is estimated by fitting a two parameter exp onential model to the background-corrected data. For two models of the back ground signal, I determine the optimal ratio of the number of "background-o nly" measurements to, the number of primary "neutron decay plus background" measurements. Further, for each run, I determine the optimal allocation of time for filling and for observing decay events. For the case where the ba ckground consists of an activated material (aluminum) plus a stationary Poi sson process, the asymptotic standard error of the lifetime estimate comput ed from the background-corrected data is lower than the asymptotic standard error computed from the uncorrected data. For the case where the backgroun d is a stationary Poisson process, background correction is desirable provi ded that the background intensity is sufficiently small compared to the rat e at which neutrons enter the trap. (C) 2001 Elsevier Science B.V. All righ ts reserved.