Difference between Quark-Gluon Plasma and Color-Glass Condensate?

Question

From the news. Apparently they are very similar, yet different.

Answer 1

OK: When a high energy collision occurs, a color-glass condensate (CGC) is formed, then a “glasma”, and then a quark-gluon plasma (QGP). This all happens very rapidly. The CGC is glassy, ie resembling a solid, but not a crystal. The glasma is very hot. The QGP has color charges instead of (or in addition to) electric charges, but other wise resembles an ordinary plasma. It is liquid-like, rather than gas-like or dust-like, as was expected before the RHIC experiments.

The CGC was expected for heavy ion collisions, but not for proton-lead collisions (at least by some authors), but it appears to be there.

All three (CGC, glasma, and QGP) can be described as “new states of matter” ala the popular press, but have been predicted, discussed (in the professional literature), and possibly observed before the recently announced LHC Alice experiments, but now are much better confirmed.

This is what I have gathered so far. My understanding is still quite shaky.

I think the relevant recent publication is this one:

http://arxiv.org/abs/1211.3701

I have now read the CGC and QGP wikipedia pages three times, including once before my first post, and I still think that they are more confusing than helpful.

(By the way, this is my first time “answering my own question”. I wouldn’t do it if I had gotten a better answer elsewhere.)

Answer 2

Nuclear matter (neutrons and protons) consist of quarks held together by gluons. Typically these bound states of either three quarks (baryons) or a quark antiquark pair (mesons) are the only quark states allowed because of something called color confinement, basically that things that have color charge are not allowed to exist on their own, the net color charge of stable things must be colorless. QCD predicts something called asymptotic freedom at high energy density and at small distance scales. the QGP is this asymptotic freedom for QCD at extreme high energy densities where the quarks and gluons are no longer confined to hadronic states but rather they behave as a fluid of quarks. Think of it like hadrons are ice and the QGP is water. The gist of the phenomena of QGP is that it behaves collectively as a fluid and not as a bunch of hadrons.

I'm writing my thesis right and I stumbled across this thread looking for info on CGC. My understanding at the moment is that the CGC describes more the behavior of ions at extremely high energies. If you were to take, say, a gold ion, and accelerate it to ultrarelativistic speeds you would get length contraction to the point that the ion would look like a disk in the lab frame. Inside the disk is a distribution of quarks and gluons in hadronic bound states. Relative to the speed of the ion, the quarks and gluons are moving within the disk very slowly, this is where the "glass" part comes in, a state of matter that is fluid in long time scales but is solid at short ones. Again this is all due to the ultrarelativistic speed of the ion. The ion also experiences time dilation. While typically quarks are held together by exchange of virtual gluons that snap into and out of existence, for ions at ultrarelativistic speeds and in the lab frame this "snapping in and out" is more or less stationary and the faster the ion goes the more gluons are "frozen" so to speak. this is the "condensate" part. The higher the energy, the more "saturated" the nucleus is with gluons that carry color charge.

Again I'm still looking for a better understanding myself but this is what Ive gathered about the CGC so far.