We evaluate the decays of a heavy neutral gauge boson $Z_2$ into $W^{+}$$W^{\mathrm{-}}$, the Z and a Higgs boson, or two Higgs bosons in superstring-inspired electroweak models with an extra U(1) gauge group, two Higgs doublets, and a Higgs singlet. The branching ratios for these processes are generally similar and two-boson decay modes of $Z_2$ must exist at the few-percent level if kinematically accessible, although the bosonic modes which dominate in any given scenario depend on the U(1) quantum numbers and mixing in the Higgs sector. Lower bounds on the $Z_2$ mass versus the Z,Z’ mixing are discussed; for the no-scale & must be above 550 GeV.

• Received 1 June 1987

DOI:https://doi.org/10.1103/PhysRevD.36.3429