This Letter reports indications of neutrino instability obtained from data taken on the charged- and neutral-current branches of the reaction ${\overline{\nu }}_e+d\{\nearrow n+n+e^{+},(\mathrm{cc}d\left)\right\}\{\searrow n+p+{\overline{\nu }}_e,(\mathrm{nc}d\left)\right\}$ at 11.2 m from a 2000-MW reactor. These results at the (2-3)-standard-deviation level, based on the departure of the measured ratio ($\frac{\mathrm{cc}d}{\mathrm{nc}d}$) from the expected value, make clear the importance of further experimentation to measure the ${\overline{\nu }}_e$ spectrum versus distance.

• Received 24 April 1980

DOI:https://doi.org/10.1103/PhysRevLett.45.1307