Theoretical models for nuclear astrophysics

by Pierre Descouvemont

Wednesday 10 Dec 2014, 14:30 → 15:30 Europe/Rome

131 (Building C, ground floor)

Energy production and nucleosynthesis in stars arise from nuclear reactions. For light elements, these reactions are essentially radiative capture and transfer. In most astrophysical scenarios, a large number of cross sections, involving protons, neutrons and alpha particles, are needed. However, as stellar energies are much lower than the Coulomb barrier, the cross sections for reactions between charged particles are in general too low to be directly measured in the laboratory. In addition, many important reactions involve short-live nuclei, which are difficult to investigate experimentally. Consequently, theoretical models are often used, either to extrapolate experimental cross sections down to stellar energies, or to evaluate cross sections when no data exist. We essentially report on two approaches: (a) microscopic cluster models, based on a nucleon-nucleon interaction, and on the assumption of a cluster structure for the nucleus; (b) the R-matrix method, where resonance properties are fitted on experimental data (capture cross sections, elastic phase shifts, etc.), and then used to predict the cross section at stellar energies. Recent examples will be presented. We also report on recent efforts to develop cross-section databases, and to provide the astrophysics community with reliable reaction rates.