Low-energy photon production in neutrino neutral-current interactions

The search for nu(mu) -> nu(e) oscillations by the MiniBooNE Collaboration at Fermilab has revealed a low-energy signal which could be due either to electrons produced by nu(e) or photons produced by the interaction of the weak neutral current on the target nucleus. One contribution to the latter is a Wess-Zumino-Witten anomaly leading to a term in the Lagrangian proportional to epsilon(mu nu kappa lambda)Z(mu)omega F-nu(kappa lambda). This term is normalized with the help of the known rates for the processes f(1) -> rho gamma and tau -> nu(tau)a(1). A rate of about 1/4 of that employed in several previous estimates is obtained. As the anomaly term had already been found to play a subdominant role in photon production (e.g., in comparison with Delta excitation and decay), the present estimate reduces its strength even further.