Final Activity Report Summary - STRINTQGP (Strong interactions in the quark-gluon plasma)
Exploration of the hadronic matter and the quark-gluon plasma, together with deconfinement transition between these two phases, is one of the great challenges in modern physics. The deconfinement phase transition is the only one in the early Universe, which can be studied experimentally, by colliding nuclei at ultra-relativistic energies. Experiments at the 'Relativistic heavy ion collider' (RHIC) at Brookhaven, performed at such energies, have led to numerous discoveries.
Altogether, they evidence that the quark-gluon plasma is strongly coupled even at temperatures as large as few times the deconfinement critical temperature in QCD. Numerical simulations of finite-temperature QCD on the lattice complement the heavy-ion experimental program. They provide a lot of new information on the nonperturbative properties of QCD in both the hadronic and the quark-gluon plasma phases.
The main objective for this project was the analysis of nonperturbative thermodynamics and kinetics of the quark-gluon plasma, as those are described by the RHIC experiments and lattice simulations. The project can be charecterised by the following keywords:
quantum chromodynamics (QCD), quark-gluon plasma, heavy-ion collisions, confinement-deconfinement phase transition, static quark-antiquark potential, QCD string-breaking in the hadronic phase, Debye screening in the quark-gluon plasma phase, chromo-magnetic gluon condensate and spatial confinement, valence gluons, QCD running coupling, event-shape variables in QCD, QCD jets, radiative energy loss and jet quenching.
Specifically, the main results were obtained in the following four directions:
1. Description of the recent lattice data on the thermodynamics of a static quark-antiquark pair at separations larger than 1.5 fermi, in the vicinity of the deconfinement phase transition.
2. The analysis of the so-called infra-red freezing (i.e. finiteness) of the running strong coupling, in the confinement and deconfinement phases of QCD.
3. Analysis of the energy loss of a parton traversing the quark-gluon plasma, which it experiences through the interactions with hard thermal gluons.
4. Studies of the degree to which the quark-gluon plasma deviates from ideality.
These results are fundamentally important for the calculation of various kinetic coefficients of the quark-gluon plasma, such as the bulk viscosity.
Altogether, they evidence that the quark-gluon plasma is strongly coupled even at temperatures as large as few times the deconfinement critical temperature in QCD. Numerical simulations of finite-temperature QCD on the lattice complement the heavy-ion experimental program. They provide a lot of new information on the nonperturbative properties of QCD in both the hadronic and the quark-gluon plasma phases.
The main objective for this project was the analysis of nonperturbative thermodynamics and kinetics of the quark-gluon plasma, as those are described by the RHIC experiments and lattice simulations. The project can be charecterised by the following keywords:
quantum chromodynamics (QCD), quark-gluon plasma, heavy-ion collisions, confinement-deconfinement phase transition, static quark-antiquark potential, QCD string-breaking in the hadronic phase, Debye screening in the quark-gluon plasma phase, chromo-magnetic gluon condensate and spatial confinement, valence gluons, QCD running coupling, event-shape variables in QCD, QCD jets, radiative energy loss and jet quenching.
Specifically, the main results were obtained in the following four directions:
1. Description of the recent lattice data on the thermodynamics of a static quark-antiquark pair at separations larger than 1.5 fermi, in the vicinity of the deconfinement phase transition.
2. The analysis of the so-called infra-red freezing (i.e. finiteness) of the running strong coupling, in the confinement and deconfinement phases of QCD.
3. Analysis of the energy loss of a parton traversing the quark-gluon plasma, which it experiences through the interactions with hard thermal gluons.
4. Studies of the degree to which the quark-gluon plasma deviates from ideality.
These results are fundamentally important for the calculation of various kinetic coefficients of the quark-gluon plasma, such as the bulk viscosity.