Neutron lifetime measured by monitored storing of ultra-cold neutrons

Quasielastic scattering in the interaction of ultracold neutrons with a liquid wall and application in a reanalysis of the Mambo I neutron-lifetime experiment

“…Measurements performed over the past few decades have stated accuracies close to 0.1% [2,3] but disagree by as much as 5 standard deviations. Explicitly, Arzumanov et al [2] quote τ n = 885.4 ± 0.9(stat) ± 0.4(sys) s, as compared to the value 878.5 ± 0.7(stat) ± 0.3(sys)s of Serebrov et al [3].…”

“…Measurements performed over the past few decades have stated accuracies close to 0.1% [2,3] but disagree by as much as 5 standard deviations. Explicitly, Arzumanov et al [2] quote τ n = 885.4 ± 0.9(stat) ± 0.4(sys) s, as compared to the value 878.5 ± 0.7(stat) ± 0.3(sys)s of Serebrov et al [3]. The experiment [1] of Mampe et al had been the first of a series of fairly high precision measurements using ultracold neutron (UCN) storage in a Fomblin-oil-coated chamber, yielding the value τ n = 887.6 ± 3 s. To separate the small UCN loss due to imperfect wall reflection from that due to β decay, the authors had used a special scaling technique for storage data extrapolation to zero wall loss and applied two corrections to the raw data extrapolation, a gravity correction and a spectral correction.…”

“…The discussions in Sec. VII review the current status of the neutron-lifetime value, taking into account also a recent revision of the 2000 double-bottle experiment [2] by the authors of that work. We also discuss the unitarity issue for the Cabibbo-Kobayashi-Maskawa quark mixing matrix, as derived from neutron measurements alone (lifetime and asymmetry parameters).…”

Magnetic trapping of ultracold neutrons

“…Several storage techniques have been used to make measurements of the neutron lifetime. The most precise storage measurements yielded values of τ n = 882.6 s ± 2.7 s [6], 888.4 s ± 3.3 s [7] and 885.4 s ± 0.9 s ± 0.4 s [8].…”

“…[7], the storage time is measured as a function of UCN velocity, and an extrapolation is made to zero velocity, or an infinite time between collisions with the walls. The most recent measurement, [8], uses two different storage-vessel sizes with neutron detectors to measure the relative rate at which neutrons are scattered out of the storage vessel in the two configurations.…”