General analysis of a possible second weak neutral current in gauge models

The most general electroweak gauge model with two weak neutral currents and no anomalies is discussed. The effective neutral-current interaction at low energies is specified by five parameters. These parameters are determined from a fit to data for the special cases of $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R\times \mathrm{U}{\mathrm{}\left(1\right)\mathrm{}}_{B-L}$ and $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times \mathrm{U}{\mathrm{}\left(1\right)\mathrm{}}_R\times \mathrm{U}{\mathrm{}\left(1\right)\mathrm{}}_{B-L}$, with and without the constraints of Higgs-boson structure. From this phenomenological analysis, the neutral-boson masses in left-right models are found to be constrained to the intervals $83<\mathrm{}{M}_{Z_1}<116\mathrm{}$ GeV and $M_{Z_2}>205\mathrm{}$ GeV. Two-$Z$ models of the type $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times \mathrm{U}\mathrm{}\left(1\right)\mathrm{}\times G$ where fermions do not transform under $G$ are obtained as another special case. An SU(2)×U(1)×U(1)′ model with identical hypercharge currents and unbounded $Z$ masses is another limiting case of the general formalism.