We examine contributions from heavy fermions to the weak radiative corrections ΔR, Δ$m_Z$, Δ$m_W$, Δρ, and Δ ${\sin }^2$${\mathrm{theta}}_{\mathrm{W}}$ in a way that is applicable to any general gauge theory. A recipe which can be followed to obtain the above-mentioned quantities for any given system of fermions is provided. Our formulas do not cover the case in which the fermion masses are too close to the W mass. Examples are given in order to illustrate the use of this recipe. Using our method we prove that any heavy vectorlike multiplet gives vanishing weak radiative corrections and, when the heavy vectorlike multiplet is coupled to an arbitrary light sector, the weak radiative corrections are given by the light sector only, up to O(1/$m_{\mathrm{heavy}{\mathrm{}}^2)}$.

• Received 12 July 1985

DOI:https://doi.org/10.1103/PhysRevD.33.1397