Near threshold expansion of Feynman diagrams

E. Mendels

doi:10.1063/1.1947119

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arXiv · hep-ph/0508234

Near threshold expansion of Feynman diagrams

E. Mendels

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Abstract

The near threshold expansion of Feynman diagrams is derived from their configuration space representation, by performing all x integrations. The general scalar Feynman diagram is considered, with an arbitrary number of external momenta, an arbitrary number of internal lines and an arbitrary number of loops, in n dimensions and all masses may be different. The expansions are considered both below and above threshold. Rules, giving real and imaginary part, are derived. Unitarity of a sunset diagram with I internal lines is checked in a direct way by showing that its imaginary part is equal to the phase space integral of I particles.

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E. Mendels. 2005-08-22. Near threshold expansion of Feynman diagrams. https://doi.org/10.1063/1.1947119

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