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Durham University

Department of Physics

Staff profile

Publication details for Simon Badger

Badger, Simon, Brønnum-Hansen, Christian, Buciuni, Francesco & O’Connell, Donal (2017). A unitarity compatible approach to one-loop amplitudes with massive fermions. Journal of High Energy Physics 2017(6): 141.

Author(s) from Durham


We explain how one-loop amplitudes with massive fermions can be computed using only on-shell information. We first use the spinor-helicity formalism in six dimensions to perform generalised unitarity cuts in d dimensions. We then show that divergent wave-function cuts can be avoided, and the remaining ambiguities in the renormalised amplitudes can be fixed, by matching to universal infrared poles in 4 − 2ϵ dimensions and ultraviolet poles in 6 − 2ϵ dimensions. In the latter case we construct an effective Lagrangian in six dimensions and reduce the additional constraint to an on-shell tree-level computation.