Detection of Weak Neutral Current Using Fission bar{ν}_{e} on Deuterons

The weak-neutral-current reaction bar{ν}_{e} + d → n + p + bar{ν}_{e} has been observed concurrently with the charged-current process bar{ν}_{e} + d → n + n + e^{+} using an Instrumented D₂O target exposed to an bar{ν}_{e} flux of 2.5×10¹³ cm^-2 sec^-1. The measured neutral-current cross section, (3.8±0.9) × 10^-45 cm²/bar{ν}_{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 cm²/bar{ν}_{e}, in fair agreement with expectation.