A framework for matrix-element-corrected QED antenna showers in hadron decays

Abstract

We present a general framework for the description of QED parton showers in hadron decays. The formalism is constructed in terms of coherent QED antennae with full dependence on particle masses and extends beyond the YFS approach by systematically incorporating spin-dependent (quasi)collinear single-unresolved limits to all orders. In addition, we incorporate corrections derived from tree-level matrix elements up to $\mathcal{O}(α^2)$ and describe a generic procedure to obtain such matrix elements using FeynRules and MadGraph. We provide an explicit implementation of the method for decays involving pseudoscalar mesons and for decays of vectors and pseudoscalars into fermion-antifermion pairs, within the combined Pythia+Vincia parton-shower Monte Carlo framework, and compare the resulting QED emission spectra to those generated with Photos and Sherpa+Photons++ through the EvtGen generator.