Interleaved resonance decays and electroweak radiation in the Vincia parton shower

Helen Brooks, Peter Skands, Rob Verheyen

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We propose a framework for high-energy interactions in which resonance decays and electroweak branching processes are interleaved with the QCD evolution in a single common sequence of decreasing resolution scales. The interleaved treatment of resonance decays allows for a new treatment of finite-width effects in parton showers. At scales above their offshellness (i.e., typically Q > γ ), resonances participate explicitly as incoming and outgoing states in branching processes, while they are effectively "integrated out" of the description at lower scales. We implement this formalism, together with a full set of antenna functions for branching processes involving electroweak (W=Z=H) bosons in the Vincia shower module in Pythia 8.3, and study some of the consequences.

Original languageEnglish
Article number101
Number of pages39
JournalSciPost Physics
Issue number3
Publication statusPublished - 22 Mar 2022

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