This is in reference to a MC generator called Pythia, but has wider applicability because the phrases are used widely in particle phyiscs, even though I have not managed to find a clear, understandable definition.
I have come across the phrase "hard process" multiple times while trying to study proton-proton collisions. My understanding of it is that any non-diffractive, non-elastic collision is a hard process. Or in loose terms, probably any event where something new is produced. Is that correct?
Secondly, Pythia coins another term - "second hard process", which too I don't understand.
Also, I am assuming that all these terms pertain only to QCD processes. Is that true?