Coulomb breakup of halo nuclei by a time-dependent method

Halo nuclei are among the strangest nuclear structures.They are viewed as a core containing most of the nucleonssurrounded by one or two loosely bound nucleons. These have a high probability of presence at a large distancefrom the core.Therefore, they constitute a sort of halo surrounding the other nucleons.The core, remaining almost unperturbed by the presenceof the halo is seen as a usual nucleus.The Coulomb breakup reaction is one of the most usefultools to study these nuclei. It corresponds to thedissociation of the halo from the core during a collisionwith a heavy (high Z) target.In order to correctly extract information about the structure ofthese nuclei from experimental cross sections, an accuratetheoretical description of this mechanism is necessary.In this work, we present a theoretical methodfor studying the Coulomb breakup of one-nucleon halo nuclei.This method is based on a semiclassical approximationin which the projectile is assumed to follow a classical trajectory.In this approximation, the projectile is seen as evolvingin a time-varying potential simulating its interaction with the target.This leads to the resolution of a time-dependent Schrödingerequation for the projectile wave function.In our method, the halo nucleus is describedwith a two-body structure: a pointlike nucleon linked to apointlike core.In the present state of our model, the interaction betweenthe two clusters is modelled by a local potential.The main idea of our method is to expand the projectile wave functionon a three-dimensional spherical mesh.With this mesh, the representation of the time-dependent potentialis fully diagonal.Furthermore, it leads to a simplerepresentation of the Hamiltonian modelling the halo nucleus.This expansion is used to derive an accurate evolution algorithm.With this method, we study the Coulomb breakupof three nuclei: 11Be, 15C and 8B.11Be is the best known one-neutron halo nucleus.Its Coulomb breakup has been extensively studied both experimentallyand theoretically.Nevertheless, some uncertainty remains about its structure.The good agreement between our calculations and recentexperimental data suggests that it can be seen as as1/2 neutron loosely bound to a 10Be core in its0+ ground state.However, the extraction of the corresponding spectroscopic factorhave to wait for the publication of these data.15C is a candidate one-neutron halo nucleuswhose Coulomb breakup has just been studied experimentally.The results of our model are in good agreement withthe preliminary experimental data. It seems therefore that15C can be seen as a 14C core in its 0+ground state surrounded by a s1/2 neutron.Our analysis suggests that the spectroscopic factorcorresponding to this configuration should be slightly lowerthan unity.We have also used our method to study the Coulomb breakupof the candidate one-proton halo nucleus 8B.Unfortunately, no quantitative agreement could be obtainedbetween our results and the experimental data.This is mainly due to an inaccuracy in the treatmentof the results of our calculations.Accordingly, no conclusion can be drawn about the pertinenceof the two-body model of 8B before an accurate reanalysis of theseresults.In the future, we plan to improve our method in two ways.The first concerns the modelling of the halo nuclei.It would be indeed of particular interest to testother models of halo nuclei than the simple two-body structureused up to now.The second is the extension of this semiclassical model totwo-neutron halo nuclei.However, this cannot be achievedwithout improving significantly the time-evolution algorithm so as toreach affordable computational times.Doctorat en sciences appliquées