DaniŽl Boer's Physics Webpage

Topic 2: Small x physics & the Color Glass Condensate

Description and objectives:

The theory called Quantum Chromodynamics (QCD) describes the physics of quarks and gluons, which are the building blocks of hadronic matter: protons, neutrons, etc. In recent years attention has turned to the behavior of QCD in extreme circumstances, such as those of high gluon density occurring in ultra-relativistic collisions between heavy ions. Theory predicts that in such collisions the gluon density in one heavy ion as seen by the particle that strikes it, will saturate forming an unusual state that has been named the Color Glass Condensate (CGC). Experiments that could be sensitive to the presence and properties of the CGC can be performed in present-day and future colliders (RHIC, LHC, EIC). Therefore, observable consequences of the CGC need to be worked out in detail. The CGC has its own characteristic momentum scale, called the saturation scale, but how to extract it unambiguously from experiment? Also, the change of the CGC with energy is predicted by theory using various approximations and limits, they all reach the conclusion that at asymptotically high energies there will be scaling behavior, geometric scaling. A main question is: is there scaling or the onset of scaling at presently accessible energies? The phenomenology of the CGC in high energy scattering at small parton momentum fraction x presents many open questions still.

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