U_e(1)--covariant R_\xi--gauge for the two Higgs doublet model

Abstract

An $U_e(1)$--covariant $R_\xi$ gauge for the two Higgs doublet model based in the BRST symmetry is introduced. This gauge allows one to remove an important number of nonphysical vertices appearing in conventional linear gauges, which greatly simplifies the loop calculations, since the the resultant theory satisfies QED--like Ward identities. The presence of four ghost interactions in this type of gauges and its connection with the BRST symmetry is stressed. The Feynman rules for those new vertices that arise in this gauge, as well as for those couplings already present in the linear $R_\xi$ gauge but that are modified by this gauge--fixing procedure, are presented.