36 research outputs found
Breakup reaction models for two- and three-cluster projectiles
Breakup reactions are one of the main tools for the study of exotic nuclei,
and in particular of their continuum. In order to get valuable information from
measurements, a precise reaction model coupled to a fair description of the
projectile is needed. We assume that the projectile initially possesses a
cluster structure, which is revealed by the dissociation process. This
structure is described by a few-body Hamiltonian involving effective forces
between the clusters. Within this assumption, we review various reaction
models. In semiclassical models, the projectile-target relative motion is
described by a classical trajectory and the reaction properties are deduced by
solving a time-dependent Schroedinger equation. We then describe the principle
and variants of the eikonal approximation: the dynamical eikonal approximation,
the standard eikonal approximation, and a corrected version avoiding Coulomb
divergence. Finally, we present the continuum-discretized coupled-channel
method (CDCC), in which the Schroedinger equation is solved with the projectile
continuum approximated by square-integrable states. These models are first
illustrated by applications to two-cluster projectiles for studies of nuclei
far from stability and of reactions useful in astrophysics. Recent extensions
to three-cluster projectiles, like two-neutron halo nuclei, are then presented
and discussed. We end this review with some views of the future in
breakup-reaction theory.Comment: Will constitute a chapter of "Clusters in Nuclei - Vol.2." to be
published as a volume of "Lecture Notes in Physics" (Springer
Experimental investigation of the 12C+12C fusion at very low energies by direct and indirect methods
The 12C+12C fusion reaction plays a crucial role during stellar evolution. The astrophysically important energy range spans from 1 MeV to 3 MeV. However, its cross section has not been determined with enough precision, despite numerous studies, due to the extremely low reaction cross sections and the large experimental background. To allow measurements of the 12C+12C fusion at astrophysical energies, we developed an efficient thick-target method using large-area silicon strip detectors. Further measurements at even lower energies will be performed using coincidences between a silicon-detector and a Ge-detector array, at the high-current accelerator under construction at the University of Notre Dame. Since the coincidence method does not allow obtaining information about the channels without gamma-ray emission, a solenoid spectrometer has been constructed for complementary measurements. Meanwhile, we are also investigating the 24Mg(α, α') reaction using the Grand Raiden Spectrometer at RCNP to search for potential resonances in the 12C+12C fusion reaction. Preliminary results from these measurements will be presented