Neutron lifetime measurement with pulsed cold neutrons

The neutron lifetime has been measured by comparing the decay rate with the reaction rate of ${}^3$He nuclei of a pulsed neutron beam from the spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC). The decay rate and the reaction rate were determined by simultaneously detecting electrons from the neutron decay and protons from the ${}^3$He(n,p)${}^3$H reaction using a gas chamber of which working gas contains diluted ${}^3$He. The measured neutron lifetime was $898\pm 10{}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}}{}_{-18}^{+15}{}_{\mathrm{s}\mathrm{y}\mathrm{s}}$s.