Is there color confinement in quarkgluonplasma?

[nonequilibrium]

Hello,

My knowledge on particle physics is very limited (halfway through my physics bachelor) but if I have to write a popular-scientific article on quarkgluonplasma (QGP) for a certain course. And I have a fair general understanding, but I was wondering if there was still color confinement in a QGP. The hadrons seem to "merge" above a certain temperature and you get some sort of quark gas (or liquid), but on the other hand "color confinement" sounds really fundamental in the way that it says that the only possible combination has to have a white color, which one quark can never have, so we can never see one quark. So can we see individual quarks in a QGP? Or is it more like as if the hadrons in the QGP formed one big hadron in which the quarks can move freely, but for the same reason as in the case of one hadron we still can't isolate one quark.

Thank you.

 

[the_house]

I'm not entirely sure what exactly your last two sentences are asking, but it seems like you probably have a fairly good handle on things.

In a quark-gluon plasma, individual quarks and gluons are no longer confined to a small area, so you typically say that you no longer have confinement above some "deconfinement" transition temperature. At the same time, the plasma is always locally color-neutral, so in that sense you still can't isolate color charge, but that's not what is usually meant by "color confinement".

If that doesn't help, you may need to clarify your question (or wait for someone else to give a better answer).

 

[tom.stoer]

... but on the other hand "color confinement" sounds really fundamental in the way that it says that the only possible combination has to have a white color ...

These wre two different issues.

Vanishing global color charge = the fact that only "white" objects are physical should be named color neutrality and can be derived from the QCD Lagrangian rather rigorously. It basically says that all physical states must have vanishing color charge - but it sais nothing about separation of colors from anticolors. Color neutrality is respected in all phases of QCD including QGP.

Color confinement says that in the IR limit you can't separate color charges from anticharges due to an effective nearly linear potential. This physical effect is caused by QCD dynamics in a certain regime. With increasing energy density QCD will undergo a phase transition from the confining phase to QGP phase, which means that in QGP color confinement is not realized. It is not a fundamental principle.