ABSTRACT

Electromagnetic gauge invariance of physical amplitudes involving the production and decay of resonances may be broken if the finite width effects are introduced in a naive way. One of the simplest cures suggested for this problem is to use the so-called complex mass scheme which consists in replacing https://www.w3.org/1998/Math/MathML"> M 2 → M 2 - iM Γ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429076619/c00d8d0d-b3a0-431a-a3c2-e044ea15f7a5/content/eq8745.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> ( M the mass and Γ the width of the resonance) in all the Feynman rules used to compute the physical amplitude. In this talk we show that this prescription is derivable from the computation of the absorptive corrections to propagators and electromagnetic vertices of resonances in the limit of massless particles appearing in loop corrections. A few examples of physical processes are provided to illustrate this point.