Ratio|gAgV|derived from the proton spectrum in free-neutron decay

The electron-neutrino angular-correlation coefficient was determined by measuring the shape of the proton recoil spectrum from free-neutron decay. The protons leaving a highly evacuated tangential reactor beam tube were analyzed by a spherical condenser spectrometer and counted in an ion-electron converter detector. The design of the apparatus, the possible disturbing influences, and the measures to reduce their effects are discussed. The remaining corrections were either calculated or determined by auxiliary measurements and applied to the spectral shape. The sources of systematic errors are considered and included in the final results. We obtained $a=-0.1017\mathrm{}\pm 0.0051$ giving $\left|\frac{g_A}{g_V}\right|=1.259\mathrm{}\pm 0.017$.