Exponentiation in QED and Quasi-Stable Charged Particles

In this note we present a new exponentiation scheme of soft photon radiation from charged quasi-stable resonances. It generalizes the well established scheme of Yennie, Frautschi and Suura. While keeping the same functional form of an exponent, the new scheme is both exact in its soft limit and accounts properly for the kinematical shift in resonant propagators. We present the scheme on an example of two processes: a toy model of single W production in e ν scattering and the W pair production and decay in e + e − annihilation. The latter process is of relevance for the planned FCCee collider where high precision of Monte Carlo simulations is a primary goal. The proposed scheme is a step in this direction.