Direct one-loop renormalization of SU(2)LxU(1)Y four-fermion processes and running coupling constants

Within the SU(2)LxU(1) electroweak theory, by combining (bosonic) vacuum polarization with vertex and box contributions, we derive gauge-invariant (one-loop) dressed propagators for the W±-boson and the γW3 system in a straightforward manner. By introducing running couplings and masses, the corresponding four-fermion amplitudes are cast into a Born term form. The subsequent 'direct renormalization' expresses the running quantities in terms of their values at a chosen scale. Among other things, the value of Δr is rederived, and a comparison of our procedure and results with the results in the literature is carried out. Care is taken to give a transparent presentation of all physically relevant steps. (orig.)