Neutron Lifetime Measurement With Pulsed Cold Neutrons

The neutron lifetime has been measured by comparing the decay rate with the reaction rate of He-3 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 He-3(n, p)H-3 reaction using a gas chamber, the working gas of which contains diluted He-3. The measured neutron lifetime was 898 +/- 10(stat) (+15)(-18)(sys) S.