Electroweak reactions with light nuclei

The investigation of light nuclei with ab-initio methods provides an optimal setting to probe our knowledge on nuclear forces, because the few-nucleon problem can be solved accurately. Nucleons interact not only in pairs but also via many-body forces. Theoretical efforts need to be taken towards the identification of nuclear observables sensitive to the less known many-nucleon forces. Electromagnetic reactions can potentially provide useful information on this. We present results on photo-absorption and electron scattering off light nuclei, emphasizing the role of three-body forces and the comparison with experimental data. On the other hand, reactions induced by weak probes, like neutrino interactions with nucleonic matter, are relevant to astrophysics and can be calculated with few-body techniques. In this case, since often no experiment is possible, ab-initio predictions provide valuable input for astrophysical simulations.Comment: 17 pages, 17 figures, Proceedings of the 19th International IUPAP Conference on Few-Body Problems in Physics, Aug. 31 - Sept. 5, 2009, Bonn, German

Emission of neutrino-antineutrino pairs by hadronic bremsstrahlung processes

We review our recent calculations of neutrino-antineutrino pair production from bremsstrahlung processes in hadronic collisions at temperature and densities relevant for core-collapse supernovae. We focus on neutron-neutron and neutron-alpha collisions.Comment: 8 pages, 4 figures, proceedings of the NN2015 conference, Catania, 21-26 June, 201

Long Range Tensor Correlations in Charge and Parity Projected Fermionic Molecular Dynamics

Within the framework of Fermionic Molecular Dynamics a method is developed to better account for long range tensor correlations in nuclei when working with a single Slater determinant. Single-particle states with mixed isospin and broken parity build up an intrinsic Slater determinant which is then charge and parity projected. By minimizing the energy of this many-body state with respect to the parameters of the single-particle states and projecting afterwards on angular momentum ground state energies are obtained that are systematically lower than corresponding Hartree-Fock results. The realistic Argonne V18 potential is used and short range correlations are treated with the Unitary Correlation Operator Method. Comparison with exact few-body calculations shows that in $^4$He about one fifth of the correlation energy due to long-range correlations are accounted for. These correlations which extend over the whole nucleus are visualized with the isospin and spin-isospin density of the intrinsic state. The divergence of the spin-isospin density, the source for pion fields, turns out to be of dipole nature.Comment: 12 pages, 4 figure