A nonlinear Rξ - gauge for the electroweak theory

A Gauge-fixing procedure for the electroweak theory, based in the BRST symmetry and covariance under the electromagnetic group, is proposed. It is found that in order to have a renormalizable theory, four-ghost interactions must be included in the BRST invariant action, since in this class of gauges these couplings are induced at the one-loop level. This type of gauges allow to remove several unphysical vertices appearing in conventional linear gauges, which greatly simplifies the loop calculations, since the resultant theory satisfies QED-like Ward identities. Explicit expressions for the Lagrangian of the bosonic sector, including the corresponding ghost term, are presented. (Author)