The activity Nuclear Physics aims to explore the behaviour of nuclear matter under extreme temperatures and densities, particularly the phase transition from hadronic matter to Quark-Gluon Plasma, which takes place at about 2000 billion degrees. Such a plasma, consisting of free quarks and gluons, existed for a fleeting moment at the birth of the Universe, about 1 microsecond after the Big Bang. This can be recreated in ultra-relativistic heavy-ion collisions in the Large Hadron Collider (LHC) at CERN and the dedicated heavy-ion experiment ALICE. In addition to providing this glimpse of the behaviour of matter immediately after the Big Bang, the project addresses other fundamental questions within Quantum Chromo Dynamics (the theory of the strong interaction), like the mechanism confining quarks in hadrons, the generation of mass in the strong interaction, and the true nature of vacuum.
The Norwegian high-energy nuclear physics community is mainly associated with the ALICE experiment at LHC and involved in analysis, instrumentation and GRID computing. The Norwegian ALICE groups' physics analysis efforts are primarily focused on exploring the interaction of heavy quarkonia and heavy quarks with the QGP and their production mechanisms in small collision systems, and the vector meson and dilepton production in photon-nucleus and photon-proton interactions. Activity members have also been involved in the BRAHMS experiment at RHIC, Brookhaven, in medical physics and space physics. The group has contributed significantly to several very successful series of data analyses from Run 1 and 2 from the LHC. Many of these have been published in highly cited ALICE papers and presented at the top international conferences in our field.