Measurement of the neutron lifetime by counting trapped protons

Abstract

The neutron lifetime ${\mathrm{\ensuremath{\tau}}}_{\mathit{n}}$ has been measured by counting decay protons stored in a Penning trap whose magnetic axis coincided with a neutron-beam axis. The result of the measurement is ${\mathrm{\ensuremath{\tau}}}_{\mathit{n}}$=893.6\ifmmode\pm\else\textpm\fi{}5.3 s, which agrees well with the value predicted by precise measurements of the \ensuremath{\beta}-decay asymmetry parameter A and the standard model.