If ghost vertices were to be calculated by SARAH 3.1 or earlier versions, it has been necessary to define the gauge fixing terms in Rξ gauge. However, since version 3.2 SARAH derives these terms automatically using the calculated kinetic terms of the Lagrangian. To this end, the condition is applied that the mixing between scalar particles and vector bosons vanishes. Afterwards, the derived gauge fixing terms are used to calculate the ghost interactions.
Since it can happen in models with an extended gauge sector that several Goldstone bosons are a mixture of the same gauge eigenstate, for each massive vector boson, the corresponding Goldstone boson has to be defined