On triple-cut of scattering amplitudes

It is analysed the triple-cut of one-loop amplitudes in dimensional regularisation within spinor-helicity representation. The triple-cut is defined as a difference of two double-cuts with the same particle contents, and a same propagator carrying, respectively, causal and anti-causal prescription in each of the two cuts. That turns out into an effective tool for extracting the coefficients of three-point functions (and higher-point ones) from one-loop amplitudes. The phase-space integration is oversimplified by using residues theorem to perform the integration on the spinor variables, via the holomorphic anomaly, and a trivial integration on the Feynman parameter. The results are valid for arbitrary values of dimensions. (c) 2006 Elsevier B.V. All rights reserved.