Aye, I mentioned them in my second paragraph :D

The actual reality of a virtual particle is a bit of an open question though from my (admittedly limited) understanding. They seem to just be a figment of the maths required to arrive at the on-shell processes. A guy I spoke to recently was rather dismissive about a particular area of research as they don’t really bother with interactions that lead to external particles. Like “Oh we can calculate gg -> gggg scattering super-duper fast compared to the old methods!” “Great, how does that help us exactly?”