Mouvement collectif et multifragmentation dans les collisions centrales du systeme Xe + Sn à 50 MeV par nucleon

Abstract : This work concerns the search of an experimental signature of a collective motion in the process of the multifragmentation of hot nuclei formed in the central collisions of the Xe+Sn System at 50 MeV/nucleon. The measurements have been performed with the multidetector INDRA. The central collisions have been selected by means of a shape variable using momenta of the fragments. The spectra and the charge distributions of the products show that most of the charged particles and fragments comes from the disintegration of an equilibrated source. A minimum value of 40 mb is given for the cross section of such a mechanism. The charge (79) and the excitation energy (12.5 MeV/nucleon) of the equilibrated source have been determined by counting and with the calorimetry method. Comparison to the predictions of a sequential binary model and a phenomenological simultaneous model have been made. Only the simultaneous disintegration is able to explain the distribution of the relative angle between fragments. The energy spectra of the fragment are correctly reproduced assuming a collective energy of 2 MeV/nucleon. No dependence of this collective energy is found respect to the charge of the fragment. However, this process of a multifragmentation with a collective energy fails to explain the properties of the light charged particles.
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Nathalie Marie. Mouvement collectif et multifragmentation dans les collisions centrales du systeme Xe + Sn à 50 MeV par nucleon. Physique Nucléaire Expérimentale [nucl-ex]. Université de Caen, 1995. Français. ⟨in2p3-00010210⟩

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