Search for three body pion decays ${\pi }^{+}\to l^{+}\nu X$

A. Aguilar-Arevalo, M. Aoki, M. Blecher +21

The three body pion decays ${\pi }^{+}\to l^{+}\nu X(l=e,\mu )$, where $X$ is a weakly interacting neutral boson, were searched for using the full data set from the PIENU experiment. An…