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Zero-threshold expansion of two-loop self-energy diagrams

F. A. Berends, A. I. Davydychev, V. A. Smirnov, J. B. Tausk

hep-pharXiv:hep-ph/9410232

Abstract

An algorithm is constructed to derive a small momentum expansion for two-loop two-point diagrams in all cases where, due to the presence of physical thresholds, there are singularities at zero external momentum. The coefficients of this ``zero-threshold'' expansion are calculated analytically for arbitrary masses. Numerical examples, using diagrams occurring in the Standard Model, illustrate the convergence of the expansion below the first non-zero threshold.

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