Penguin and box diagrams in unitary gauge
Journal
European Physical Journal C
Journal Volume
64
Journal Issue
4
Pages
681-687
Date Issued
2009
Author(s)
Abstract
We evaluate one-loop diagrams in the unitary gauge that contribute to flavor-changing neutral current (FCNC) transitions involving two and four fermions. Specifically, we deal with penguin and box diagrams arising within the standard model (SM) and in nonrenormalizable extensions thereof with anomalous couplings of the W boson to quarks. We show explicitly in the SM the subtle cancellation among divergences from individual unitary-gauge contributions to some of the physical FCNC amplitudes and derive expressions consistent with those obtained using R ξ gauges in the literature. Some of our results can be used more generally in certain models involving fermions and gauge bosons which have interactions similar in form to those we consider. © 2009 Springer-Verlag/Società Italiana di Fisica.
Type
journal article