Determining Strong Phase of $a_1$ Meson Decay Amplitude using $W\to \nu \tau (\to \nu a_1(\to {\pi }^{\mp }{\pi }^{\mp }{\pi }^{\pm }))$ Process

Kaoru Hagiwara, Hiroyuki Ishida, Toshifumi Yamada +1

To measure the helicity of a spin-1 meson from the triple vector product of the three-momenta of its decay products, one needs information about the strong phase of the decay ampli…