Problems with the Breitenlohner-Maison γ 5-scheme in flavour changing neutral currents

• Published in: Physics letters. B Vol. 261; no. 1; pp. 123 - 126
• Main Authors: Barroso, A., Doncheski, M.A., Grotch, H., Körner, J.G., Schilcher, K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 23.05.1991
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/0370-2693(91)91336-T

We calculate the flavour changing neutral current (FCNC) decay Z → Q q ̄ at one-loop order using two different γ 5-prescriptions, namely the Breitenlohner-Maison-'t Hooft-Veltman (BM) γ 5-scheme and a naively anticommuting γ 5. The results obtained in the two schemes differ from one another. The BM γ 5-scheme calculation violates the conventional Ward identity relating the Z → Q q ̄ and the unphysical scalar φ z → Q q ̄ proper vertices which the naive γ 5-calculation satisfies. Hence, we conclude that it is incorrect to naively apply the BM γ 5-scheme if the standard model is renormalized on-shell.