Study of the transport and equilibration properties of nuclear matter in the Fermi energy domain.

Summary The equation of state of nuclear matter is an essential tool in the description of collisions between heavy ions, but also in the description of the formation of objects or astrophysical phenomena (structure of neutron stars, fusion of neutron stars). Establishing the equation of state of the nuclear matter requires a precise definition of the thermodynamic conditions (density, temperature, proton/neutron asymmetry) in which the system evolves. In this work, we address the problem of the maximum equilibrium state that is reached in heavy ion collisions, in terms of energy and isospin, using the INDRA multidetector experimental database built by the collaboration over the last 25 years, focusing on central collisions in the Fermi energy range, between 10 and 100 MeV/nucleon. We present in this paper how, with the help of dedicated simulations, it has been possible to relate the stopping power of nuclear matter to the nucleon-nucleon collision cross section in nuclear matter. We also bring some answers to the question of isospin transport in central collisions using the A = 3 isobaric ratios constructed from tritons and helium-3. These different results allow us to highlight the new experimental device set up by the INDRA and FAZIA collaborations: the FAZIA multi-detector. The FAZIA multi-detector is the result of a ten-year research and development period, which led to a multi-detector with its own digital electronics in a vacuum, with increased identification performance (measurement of the charge Z and mass A up to Z = 25) compared to the multi-detectors of previous generations.