h3QCD (high energy, high density and hot QCD)
ECT*, Trento, June 17-21, 2013
Description and main objectives
The main objective of the ongoing heavy ion programs at RHIC and the LHC is the exploration of new phases of
nuclear matter which are characterized by high parton densities and strong collective behavior. One of
these phases, the Color Glass Condensate, refers to the wavefunctions of the energetic hadrons (protons or
nuclei) prior to the collision: the QCD evolution with increasing energy leads to a rapid rise in the density of
low-momentum gluons, which is eventually tamed by non-linear effects leading to gluon saturation. When this happens, the
occupation number of these soft gluons is so high that a semi-classical description in terms of classical
color fields becomes appropriate. In the case of nucleus-nucleus collisions, these classical
fields preserve their coherence during the very early stages of the collision, where they extend between the
remnants of the two nuclei in the form of color flux tubes. This transient form of dense, coherent matter is known as
the Glasma.
These flux tubes are unstable and rapidly break into partons that strongly
interact with each other because of their high density. These interactions are expected to lead to a state of local
thermal equilibrium, the Quark Gluon Plasma. Experimental results suggest that this equilibration is
extremely fast and that the ensuing plasma exhibits strong coupling aspects, such as a very low viscosity-to-entropy
ratio. These phenomena are insufficiently understood and call for further studies.
Furthermore, it is possible to measure
the local properties of the quark-gluon plasma by studying its interactions with a "hard probe" -- an energetic parton or jet
that loses energy while propagating through the medium. The accompanying phenomena (energy loss, transverse
momentum broadening, jet collimation...) are known as "jet quenching".
The purpose of this workshop is to allow for in-depth discussions of various theoretical and phenomenological aspects of
the dense partonic stages of hadronic and nuclear collisions. By the time of the workshop, many results of the proton-lead
run at the LHC (scheduled
early 2013) should be available and allow for a better disentanglement between "initial-state interactions" like
saturation and "final-state interactions" like jet quenching. The workshop should provide the opportunity to
critically examine our current theoretical understanding of the initial state effects in view of the p-Pb data. Other
expected highlights of the workshop include recent theoretical progress in understanding thermalization, strong
coupling aspects of the quark-gluon plasma, and medium-induced jet evolution.
Organizers
François Gelis (CEA/IPhT) | Edmond Iancu (CEA/IPhT) | |
Cyrille Marquet (CERN) | Dionysis Triantafyllopoulos (ECT*, coordinator) |