# Etude des noyaux a halo de $^{11}$Be et $^{11}$Li par reactions de cassure du coeur

Abstract : The study of light nuclei with large neutron excess are very useful for the understanding of nuclear matter far from stability. The neutron halo phenomenon has been observed for the first time for Z < 10 nuclei in 80's : halo nuclei consist of a "stable" core (neutron separation energy of about a few MeV) and one or two neutrons with a very low separation energy of about a few hundred keV. Their wave functions can extend from the core at distances larger than the main range of nuclear force. These halo nuclei have been studied by dissociation reactions in which the neutron from the halo is detected in coincidence with the core. It has been shown that the extraction of the halo wave function is strongly influenced by (i) the reaction mechanism itself (ii) final state interactions. In the present work, I used the core breakup reactions in which the halo neutron is detected in anti-coincidence with the core to study the "Be and nLi halo nuclei. In this channel, the neutron is supposed not participate to the reaction and then, when detected, to carry out the same properties as in the halo nucleus. The deduced widths of the neutron momentum distributions are different from the one extracted from dissociation reactions. Nevertheless, they are in agreement with results extracted from the core distributions and with the more recent theoretical models. From these studies, it is also stressed that the properties of the core are essential to understand the halo phenomenon. In particular, the correlation between the core vibrations and the halo neutron are able to explain the emergence of the halo in nBe.
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S. Grevy. Etude des noyaux a halo de $^{11}$Be et $^{11}$Li par reactions de cassure du coeur. Physique des Hautes Energies - Expérience [hep-ex]. Université Paris Sud - Paris XI, 1997. Français. ⟨in2p3-00014884⟩

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