One-loop integrals in axial-type gauges

A general formula for momentum-space integrals containing one noncovariant denominator is derived. These denominators arise in ghost-free gauges such as the axial gauge. The method works in dimensionally regularized Minkowski space and employs Feynman parameters as well as the Wick rotation. The pole in the noncovariant denominator is circumvented by a general $i\epsilon$ prescription. With the final formula the principal value can also be evaluated. Several explicit examples are considered.