We calculate the flavour changing neutral current (FCNC) decay Z → Q q ̄ at one-loop order using two different γ5-prescriptions, namely the Breitenlohner-Maison-'t Hooft-Veltman (BM) γ5-scheme and a naively anticommuting γ5. The results obtained in the two schemes differ from one another. The BM γ5-scheme calculation violates the conventional Ward identity relating the Z → Q q ̄ and the unphysical scalar φz → Q q ̄ proper vertices which the naive γ5-calculation satisfies. Hence, we conclude that it is incorrect to naively apply the BM γ5-scheme if the standard model is renormalized on-shell.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics