Evidence for coherent neutral-pion production by high-energy neutrinos

We have observed a signal of 55 isolated -conversion pairs produced in a wide-band neutrino beam using the Fermilab 15-ft bubble chamber filled with a heavy Ne-H2 mixture. The signal is consistent with coherent neutral-current single-0 production followed by decay of the 0 with one of the decay 's being lost. This signal corresponds to a rate of (2.0 0.4) × 10-4 of the total charged-current cross section at our average E of 20 GeV. From this result, we obtain a value of =0.980.24 for the weak-neutral-current isovector axial-vector coupling. © 1986 The American Physical Society.