First collisions at the LHC with unprecedented Energy! (Ask a particle physisicist)

[Alex K]

QCD: indeed, QCD has the curious property that the interaction becomes stronger at large distances/low energies, which makes studying it much harder. Why QCD has this property is hard to explain visually. Possibly because I don't understand it well enough. Maybe this: the larger the distance and the longer one waits, the more time the virtual particles between say two quarks have to build up force. It indeed ends up looking like a sticky mass of glue between them.

I need to buy a better intuition plug-in.

If the interaction is stronger at larger distances, shouldn't the amount of work needed to remove the particles (quarks?) away from one another make the far apart particle condition one of higher (internal) energy?  Or isn't the interaction one of binding the particles together?  I'm confused about what high/low energy means in this context.

That is a very smart question. So yes, on the one hand, by investing higher energy one can probe shorter distances and finds that the internal energy of the binding one observes in the process becomes - less!, and therefore quickly so much less than the energy you put into the whole reaction as to become irrelevant ("asymptotic freedom of the quarks at high collision energies"). If you invest less energy into the collision, you will probe physics at larger distances and will see interactions with, oddly, larger binding energy, so the binding energy goes up if you put less energy in. At some point, this binding energy will grow beyond the energy you put into the system to make the observation in the first place. At that point, you will for this reason stop resolving the quarks, and will only see protobs, neutrons...