main purpose of the build: validation Pythia8.309 contains MRs: https://gitlab.cern.ch/atlas/athena/-/merge_requests/62060 Remove the AlpGen-specific debug output https://gitlab.cern.ch/atlas/athena/-/merge_requests/62101 Use const ref argument for HepMC::set_signal_process_vertex https://gitlab.cern.ch/atlas/athena/-/merge_requests/62182 Removal of unused or commented headers. https://gitlab.cern.ch/atlas/athena/-/merge_requests/62183 Use more const reference access for MC objects https://gitlab.cern.ch/atlas/athena/-/merge_requests/62224 Use more access by const reference for MC truth objects https://gitlab.cern.ch/atlas/athena/-/merge_requests/60831 Use the position of the vertex instead of barcode https://gitlab.cern.ch/atlas/athena/-/merge_requests/62140 Avoid duplication of attributes already serialized in other way https://gitlab.cern.ch/atlas/athena/-/merge_requests/62236 Avoid temporary objects in hepmcparticlelink if possible https://gitlab.cern.ch/atlas/athena/-/merge_requests/62250 TruthJetFilter: downgrade INFO messages to DEBUG