Electron-Neutrino Angular Correlation in the Beta Decay ofNe19

Abstract

The electron-neutrino angular correlation coefficient $\alpha$ has been determined in the beta decay of ${\mathrm{Ne}}^{19}$ by observing the spectrum of positrons coincident with nuclear recoils emitted approximately antiparallel to the positrons. The source region in the volume containing the ${\mathrm{Ne}}^{19}$ activity was defined by a retarding grid system and by the requirement that coincident recoils from the source exhibit the correct delay relative to the positrons. Negatively charged recoils were detected in a silver-magnesium alloy electron multiplier, which was also found to be fairly sensitive to uncharged recoils in the energy range below two hundred electron volts. Positron energies were determined with a crystal-photomultiplier spectrometer and multichannel analyzer. Comparison of the measurements with calculated spectra yields a value of $\alpha =-0.15\mathrm{}\pm 0.2$, confirming earlier conclusions that the beta interactions has the form $\mathrm{ST}\left(P\right)\mathrm{}$ rather than $\mathrm{VT}\left(P\right)\mathrm{}$.