Evidence for Parity Nonconservation in the Weak Neutral Current

Measurements of $R^{\nu }$ and $R^{\overline{\nu }}$, the ratios of neutral current to charged current $\nu$ and $\overline{\nu }$ cross sections, yield neutral current rates for $\nu$ and $\overline{\nu }$ that are consistent with a pure $V-A$ interaction but 3 standard deviations from pure $V$ or pure $A$, indicating the presence of parity nonconservation in the weak neutral current.