Simulation of QED Radiation in Particle decays using the YFS Formalism

In this paper we describe a program (SOPHTY) implementing QED corrections to decays in the HERWIG++ event generator. In order to resum the dominant soft emissions to all orders, the program is based on the YFS formalism. In addition, universal large collinear logarithms are included and the approach can be systematically extended to incorporate exact, process specific, higher order corrections to decays. Due to the large number of possible decay modes the program is designed to operate, as far as possible, independently of the decay matrix elements.