Extra neutral gauge boson and the processes e+e--->ZiHa in a superstring-inspired model.

Abstract

We discuss the processes ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${Z}_{i}$${H}_{a}$ (i=1,2; a=1,2,3) in a superstring-inspired model involving two Higgs-boson doublets and one singlet, and also an additional neutral gauge boson (${Z}_{E}$), at CERN LEP II and higher energies. Our main result is that, for ${Z}_{2}$ sitting on resonance at LEP II energy, the total cross section for the process ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${Z}_{1}$${H}_{2}$ is significantly large as compared with those for ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${\ensuremath{\mu}}^{+}$${\ensuremath{\mu}}^{\mathrm{\ensuremath{-}}}$, ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${W}^{+}$${W}^{\mathrm{\ensuremath{-}}}$. For ${Z}_{2}$ at off resonance, the cross sections are almost the same as that for the standard model.