Neutrino-antineutrino transitions

We consider transitions between neutrinos and antineutrinos in laboratory experiments in five scenarios. These include the case in which the helicity flips, producing an antineutrino with normal weak interactions, and helicity preserving oscillations into an (Formula presented) singlet state which only interacts by mixing or new interactions. The ratio of (Formula presented) and (Formula presented) events for a high energy (Formula presented) beam from pion decay rescattered from a nucleon target and the ratio between (Formula presented) and (Formula presented) events for a rescattered low energy (Formula presented) beam are calculated in each case. The upper limit on the ratio is about (Formula presented) for a high energy (Formula presented) beam and (Formula presented) for a low energy (Formula presented) beam, too small to observe in present experiments.