Bimodality and others signatures of liquid-gas phase transition of nuclear matter

Nuclear matter must present a liquid-gas phase transition at intermediate energies. This thesis is a study of this transition with binary collisions of symmetrical systems Xe+Sn and Au+Au from 60 to 100 MeV/u, detected with INDRA multidetector. A possible signature of liquid-gas phase transition is the observation of a bimodal distribution for an order parameter. Bimodality is a robust signal and can differentiate two family of event: the liquid phase and the gas one. This study is made on the quasi-projectile source with an asymmetry variable between the two heaviest decay products. The sorting of the event is provided by the perpendicular energy of the light charged particles emitted on the quasi-target side. Delta-scaling and negative heat capacity are also interpreted as a possible signature of phase transition. For the first one, we observe scaling law of heaviest fragment distributions for each phase. For the second one, fluctuations of the sharing of the available energy in the system can lead to a negative branch of heat capacity which is a theoretical signature of the transition. Correlation between all this observables are clearly demonstrated. A possible contribution of dynamical effect is tested and quantified with the generator of event HIPSE. The conclusion reveals a definite coherence between all signals of a phase transition. (author)