Kinetic mixing and symmetry breaking dependent interactions of the dark photon

Understand

We examine spontaneous symmetry breaking of a renormalisable U(1) x U(1) gauge theory coupled to fermions when kinetic mixing is present.

• We do not assume that the kinetic mixing parameter is small.
• A rotation plus scaling is used to remove the mixing and put the gauge kinetic terms in the canonical form.
• Fermion currents are also rotated in a non-orthogonal way by this basis transformation.