When calulating near resonant cross sections one usually inserts a mass width in the denominator of the propagator. This should, at least as I have understood it, correspond to taking the higher order diagrams into account.(adsbygoogle = window.adsbygoogle || []).push({});

What I would like to see is a proof for the equivalence between inserting a mass width and calculating the process to higer orders. Anyone's got a reference to this?

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# Mass width in the propagator?

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