Resonance- and width-aware parton shower evolution and NLO matching

A bstract We introduce a technique for the next-to-leading order accurate simulation of $${e}^{+}{e}^{-}\\to {W}^{+}{W}^{-}b\\overline{b }$$ that respects the resonant nature of the process above and near the top-quark pair production threshold. The parton-shower evolution, infrared subtraction and NLO matching account in particular for finite width effects beyond those considered in resonance-aware approaches. We present first phenomenological results relevant to a potential future electron-positron collider and provide a publicly available simulator based on the Alaric parton shower and the S herpa event generator.