AMA | September 2024

5502.433 - 5526.295 Sean Carroll

But number two, you have the strong interactions. As soon as you make quarks or gluons— then those particles interact strongly. So that quark-antiquark pair that can be produced by the traveling photon will themselves scatter gluons back and forth and other quark-antiquark pairs. And that turns out to be hard to actually calculate. And it's not just photons spitting off of the muon.