Detection of Weak Neutral Current Using Fissionν¯eon Deuterons

The weak-neutral-current reaction ${\overline{\nu }}_e+d\to n+p+{\overline{\nu }}_e$ has been observed concurrently with the charged-current process ${\overline{\nu }}_e+d\to n+n+e^{+}$ using an instrumented ${\mathrm{D}}_2$O target exposed to an ${\overline{\nu }}_e$ flux of 2.5×${10}^{13}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$. The measured neutral-current cross section, (3.8±0.9)×${10}^{-45\mathrm{}}$ ${\mathrm{cm}}^2$/${\overline{V}}_{\mathrm{e}}$, is consistent with the Weinberg-Salam model, dependent in this case only on the axial-vector contribution. The charged-current reaction cross section is (1.5±0.4)×${10}^{-45\mathrm{}}$ ${\mathrm{cm}}^2$/${\overline{V}}_{\mathrm{e}}$, in fair agreement with expectation.