Weak neutral currents in electron and muon scattering

Contributions to inelastic scattering arising from the interference of a weak neutral current with the electromagnetic current are calculated using the Weinberg model and the quark-parton model. These interferences produce nonvanishing ($d{\sigma }^{-}-d{\sigma }^{+}$), ($d{\sigma }^{-\left(L\right)\mathrm{}}-d{\sigma }^{+\left(R\right)\mathrm{}}$), ($d{\sigma }^{-\left(L\right)\mathrm{}}-d{\sigma }^{-\left(R\right)\mathrm{}}$), which give rise to sizable effects when compared to the purely electromagnetic scattering.