The study of nuclear reactions aims at describing the mechanisms sustaining the evolution of nuclear matter when it undergoes a modification of its state. This modification can occur after an external excitation (e.g., neutron capture) or internal excitation (e.g., beta decay). This evolution is the consequence of the dynamics of nucleons in interaction with its neighbours and of the reorganization of the nuclear structure.
The complexity of these reactions is inherent to the modeling of the dynamics of an N-body quantum system in strong interaction. At high energy, the nuclear structure effects disappear and the quantum framework can be approximated by classical laws. At lower energy, it is no longer possible to neglect the quantum nature of the nucleons and the modeling is more complex. Nowadays, the so-called ab-initio approaches are still far from being able to describe accurately phenomena in which the role of nuclear structure is very important, as in the case of neutron-nucleus interaction at very low energy where resonances appear in the cross sections or in the case of fission. Measurements are therefore essential and modelling approaches are more phenomenological or effective using diffusion theory and notions of thermodynamics of complex systems.
DPhN is interested in the most basic reactions such as those induced by a neutron, a proton, or by the (beta) decay of a neutron to a proton, and by the characterization of the reaction products. These reactions are of interest to characterize the interaction process of the nucleon-nucleus system and are also at work in a number of macro-systems such as nuclear reactors, stellar nucleosynthesis. They are also directly used for specific applications of radiotherapy, production of radioelements ... and are therefore of interest for all these applications.
The research program focuses on three topics:
It covers a wide energy domain (from meV to GeV) taking advantage of major and complementary intense neutron sources in Europe:
These measurements aim to characterize with very high resolution the capture and fission cross sections at low energy, the fission process and the beta decay. This program is complemented by the development of models to describe these processes up to GeV.