We present a brief review of recent theoretical developments and related phenomenological approaches for understanding the initial state of heavy-ion collisions, with emphasis on the Color Glass Condensate formalism.
I present the state of our understanding of the QCD dynamics at play in the parton saturation regime of nuclear wave functions. I explain what are the biggest open questions in the field, their intrinsic interest, but also why is it important to answ
er them from the quark-gluon-plasma physicists perspective. Focusing on those aspects that proton-nucleus collisions cannot investigate to a satisfactory degree, I show that future high-energy electron-ion colliders have the potential to address these questions, providing thorough answers in most cases, and exploratory measurements otherwise.
The possibility to measure jet-gap-jet final states in double-Pomeron-exchange events at the LHC is presented. In the context of the ATLAS experiment with additional forward physics detectors, cross sections for different experimental settings and ga
p definitions are estimated. This is done in the framework of the Forward Physics Monte Carlo interfaced with a perturbative QCD model that successfully reproduces standard jet-gap-jet cross sections at the Tevatron. The extrapolation to LHC energies follows from the Balitsky-Fadin-Kuraev-Lipatov dynamics, implemented in the model at next-to-leading logarithmic accuracy.
RHIC experiments have recently measured the azimuthal correlation function of forward di-hadrons. The data show a disappearance of the away-side peak in central d+Au collisions, compared to p+p collisions, as was predicted by saturation physics. Inde
ed, we argue that this effect, absent at mid-rapidity, is a consequence of the small-x evolution into the saturation regime of the Gold nucleus wave function. We show that the data are well described in the Color Glass Condensate framework.
I discuss novel QCD phenomena recently observed in p+p, p+A and A+A collisions, that result from the non-linear dynamics of small-x gluons. I focus on di-hadron correlation measurements, as opposed to single-hadron observables often too inclusive to
distinguish possible new effects from established mechanisms. Specifically, I discuss angular correlations of forward di-hadrons in d+Au collisions and long-range rapidity correlations in high-multiplicity p+p and Au+Au collisions.
Using the AdS/CFT correspondence, we compute the medium-induced energy loss of a decelerating heavy quark moving through a strongly-coupled supersymmetric Yang Mills plasma. In the regime where the deceleration is small, a perturbative calculation is
possible and we obtain the first two corrections to the energy-loss rate of a heavy quark with constant velocity. The thermalization of the heavy quark is also discussed.
We study the production of Mueller-Navelet jets at hadron colliders in the Balitsky-Fadin-Kuraev-Lipatov (BFKL) framework. We show that a measurement of the relative azimuthal angle DeltaPhi between the jets can provide a good testing ground for corr
ections due to next-leading logarithms (NLL). Besides the well-known azimuthal decorrelation with increasing rapidity interval Deltaeta between the jets, we propose to also measure this effect as a function of R=k_2/k_1, the ratio between the jets transverse momenta. Using renormalisation-group improved NLL kernel, we obtain predictions for dsigma/dDeltaeta dR dDeltaPhi. We analyse NLL-scheme and renormalisation-scale uncertainties, and energy-momentum conservation effects, in order to motivate a measurement at the Tevatron and the LHC.
