Appendix B: Feynman Rules for the Electroweak Theory

Abstract

Cabibbo-Kobayashi-Maskawa matrix elements V ji need to be attached to a quark pair of flavor j and i. The photon couples to the electromagnetic currents with charge Q f e and is of vector type. The Z boson couples to the neutral current which is a mixture of the left-and right-handed fermions. The coupling constants are product of a common coupling constant g Z D e sin θ W cos θ W (B.2) and flavor dependent coupling constants L (f) D I 3 f Q f sin 2 θ W , R (f) D Q f sin 2 θ W (B.3a) where f D l D e, µ, τ or f D q D u, d, s, c, b, t. Sometimes, separations according to vector and axial vector couplings are used.