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Study of ground state properties of halo nuclei via quasi-free scattering reactions
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The main goal of this work was the analysis and interpretation of experimental data obtained for the reaction (p,pn) of the one neutron halo nucleus 15C on a proton target. The measurement, performed at the GSI laboratory, was part of an experimental campaign (Experiment S393) of the R3B collaboration and the first step towards the measurement of fully exclusive reaction cross sections on exotic nuclei.
The so-called halo nuclei are of high interest as they consist of bound nuclei characterized by one or more valence nucleons orbiting at larger distances from a core. These are novel quantum systems appearing at the limits of the dripline. Furthermore, halo nuclei are characterized by low separation energies, resulting in very narrow momentum distributions of the core in nucleon knockout reactions at relativistic energies.
One neutron-halo nucleus of particularly high interest is 15C, which has a neutron separation energy of Sn = 1.218 MeV. Ground state and spectroscopic information have been extracted experimentally from Coulomb dissociation studies resulting in a consistent picture with a dominant (14C(0+) x 2s1/2) configuration. Momentum distributions of the core extracted from single neutron knockout reactions exhibited a width of 67 MeV/c, consistent with larger separation energy and the same dominant configuration. However, calculations failed to reproduce the tail of the measured momentum distributions. The momentum distributions are inclusive measurements and thus it is desirable to measure exclusive observables which incorporate more physics information.
The Faddeev/AGS formalism is a non-relativistic three-body multiple scattering framework that treats equally all opening channels (elastic, breakup and transfer) and has been used to assess the validity of approximations considered in traditional scattering frameworks. This has highlighted that traditional reaction approaches may not be adequate to study the nuclei under consideration. It was also successfully applied to the study of reactions involving halo nuclei as well as light/medium nuclear systems.
The 15C case, due to its dominant ground state configuration of 14C core in its ground state and a s-wave valence neutron (14C(0+) x 2s1/2), constitutes a very suitable case to apply the Fadeev/AGS reaction formalism to the study of the 15C.
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Halo nuclei nuclear structure quasi-free scattering neutron knockout reactions