Review of Recent Developments in the CGC

Abstract

I review recent developments in the CGC approach to high-energy collisions. The focus is on topics related to the Quark Matter conference, specifically on predictions for the p+Pb run at the LHC; as an added bonus some of these predictions are confronted with first data taken during the p+Pb machine performance test at the LHC performed in september 2012. I also highlight recent work related to particle production fluctuations, suppression of nuclear modification factors in p+A from rcBK evolution, (partial) NLO corrections in forward production, and photon-hadron as well as di-hadron correlations.Comment: 8 pages; plenary talk given at Quark Matter 2012, August 13-18, 2012, Washington DC; submitted to NP

Exploring the origin of small−x saturation in the collinear approach

“…They are treated as the phenomenological parameters in numerical simulations and shoud be estimated in the other models for further applications. The phenomena of saturation and slowing down an increase of gluon density take place also in the CGC scenario [13,[15][16][17][18]. However, the saturation scale is energy dependent in that approach and, nevertheless, it comes about quite predictive.…”

“…The origin of this freezing scale is similar to the saturation scale in the color glass condensate (CGC) approach [13,[15][16][17][18]21].…”

“…In fairness, remember it has been long time ago [9,10] argued that eventually the system under consideration should enter a new regime, where the rate of growing gluon density slows down and saturates possibly curing, thus, a potential conflict with unitarity of the underlying scattering. Actually, the restoration of the unitarity in high energy limit of QCD remains a challenging problem, although several approaches, drawing a scenario with nonlinear behavior, are being explored in past years (see, for example, [11][12][13][14][15][16][17][18] and references therein) but those allow us to conclude only that we are still no essentially closer to knowing where the problem solution lies besides of very general claim about the nonperturbative finite density effects which are left out entirely from the BFKL evolution. The interest in physics of high density regime of small x QCD is greatly increasinng and dictated by an avalanche of experimental data on collisions of relativistic heavy ions overwhelming this area of research in the last decades.…”