Théorique, numérique
In 2022, the Large Hadron Collider (LHC) has started its third run of operations. Besides precision studies of the Standard Model and searches of new physics, another goal of this experimental program is the study of the quark-gluon plasma (QGP), a new phase of nuclear matter that exists at high temperature or density, and in which the quarks and gluons are deconfined. To probe the properties of the QGP, a very useful class of observables refers to the propagation of energetic jets. A jet is a collimated spray of particles generated via successive parton branchings, starting with a virtual parton produced by the collision. When such a jet is produced in the dense environment of a nucleus-nucleus collision, its interactions with the surrounding medium lead to a modification of its properties, a phenomenon known as jet quenching. However, despite a lot of theoretical efforts in the recent years, quantitative extractions of QGP properties from jet quenching observables are still lacking. This is mainly due to large theoretical uncertainties in the calculation of the decay of a highly virtual particle in a dense QCD medium. In order to address this question, the general purpose of this PhD is to formulate the problem of the radiation of a virtual particle in a dense QCD medium in a open quantum system formalism. The PhD will take place inside the Theory group of Subatech in Nantes. The three-year position will be financed by IMT-Atlantique and attached to the 3MG graduate school.