Near threshold expansion of Feynman diagrams

2005/07/01 by E. Mendels
Mathematics · Physics and Astronomy · #Algebraic and Geometric Analysis #Particle physics theoretical and experimental studies #Quantum and Classical Electrodynamics #hep-ph

paper · pdf · doi:10.1063/1.1947119

published as J.Math.Phys. 46 (2005) 072308 · 57 pages, 7 figures

openalex publication_date 2005/07/01 · arxiv created 2005/08/22 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28

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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