Penguin and box diagrams in unitary gauge

Xiao Gang He, Jusak Tandean, G. Valencia

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12 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)681-687
Number of pages7
JournalEuropean Physical Journal C
Issue number4
Publication statusPublished - Dec 2009
Externally publishedYes

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