\begin{aligned} \textrm{Br}(Z' \rightarrow \ell \bar{\ell })&=\frac{g_\textrm{BL}^2}{12\pi } \frac{m_{Z'}}{\varGamma _{Z'}}\left( 1-4y\right) ^{1/2} \left( 1+2 y\right) \nonumber \\ \textrm{Br}\left( Z' \rightarrow \sum _i\nu _i \bar{\nu }_i \rig...