Signatures of an extra Z0 gauge boson in elastic e--proton scattering.

Abstract

We consider popular extensions of the standard model which include new heavy ${Z}^{0}$ gauge bosons, and examine their effect on parity violation in elastic electron-proton scattering at intermediate energies. These extensions all involve an effective low-energy symmetry group SU(3${)}_{\mathrm{C}}$\ensuremath{\bigotimes}SU(2${)}_{\mathrm{L}}$ \ensuremath{\bigotimes}U(1${)}_{\mathrm{Y}}$\ensuremath{\bigotimes}(U)${1}_{\mathrm{Y}\mathcal{'}}$. In several special cases motivated by grand unified theories based on SO(10) and ${\mathrm{E}}_{6}$, we find that a parity measurement with an accuracy of a few percent would raise the existing mass bounds on a heavy ${Z}^{0}$, and would reduce the range of allowed mixing angles by as much as a factor of 5. In some cases, the lower bound on a heavy ${Z}^{0}$ mass would be raised by more than 100 GeV over current limits.