Probing new gauge-boson couplings via three-body decays

We examine the possibility of using rare, three-body decays of a new neutral gauge boson $Z_2$ to probe its gauge couplings at hadron colliders. Specifically, we study the decays $Z_2\to \mathrm{Wl}\nu$ and $Z_2\to Z\nu \overline{\nu }$ and find that much knowledge of the $Z_2$ properties can be obtained from these processes. In particular, these decay modes can yield valuable information on the amount of $Z_1-Z_2$ mixing, on the generation dependence of the $Z_2$ couplings, and on the properties of the new generator associated with the $Z_2$, as well as being used to distinguish between possible extended models. Standard model backgrounds to these three-body decays are discussed, and we find that the rate for $\mathrm{pp}\to \mathrm{ZZ}\to Z\nu \overline{\nu }$ eclipses that of $\mathrm{pp}\to Z_2\to Z\nu \overline{\nu }$ at hadron supercolliders. The analogous three-body decays into a new, heavy charged gauge boson, $Z_2\to W_2^{\pm }{l}^{\mp }\nu$, are also investigated in models where this can occur.