Isospin Mixing Impurities and Magnetic Moments Close to the N = Z Line

One of the major topics of interest in experimental nuclear physics is the investigation and understanding of the fundamental properties of exotic nuclei with a neutron to proton ratio that differs significantly from that of stable nuclei. Only if these properties are understood and explained by nuclear models, can we have a better understanding of the nuclear forces holding nucleons together in an atomic nucleus.In order to contribute to this understanding, two nuclear properties that provide useful information about nuclear structure are studied in this work. Firstly, isospin mixing in nuclei close to the N=Z line was studied. Isospin is an important concept of hadron physics and was introduced in nuclear physics as an important tool for the classification of nuclear and hadronic states. There is currently great interest in the measurement of the size of isospin mixing in heavy nuclei which is expected to increase rapidly with nuclear mass along the N=Z line. This interest has recently intensified because of the impact of our understanding of nuclear isospin mixing on a unitarity test of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. Available data suggest that CKM-matrix fails the unitarity test pointing to the physics beyond the standard model. Secondly, the nuclear moments of the studied nuclei were measured. The magnetic dipole moment is sensitive to the single particle structure of the nucleons inside the nucleus, which can be directly compared to the predictions of nuclear models, allowing the testing of the validity of these models under extreme conditions (isospin, spin, and excitation energy). Nuclei decaying through pure Gamow-Teller beta-decay are polarized using the Low Temperature Nuclear Orientation Technique (LTNO). The angular distribution of the beta-particles emitted during the radioactive decay of the nuclei is measured. From the asymmetry parameter (A), the contribution of the isospin forbidden Fermi contribution in the decay can be established, yielding the amount of isospin mixing. The magnetic moments were measured using Nuclear Magnetic Resonance on Oriented Nuclei (NMR/ON). To get the required precision of the experimental results, systematic effects have to be taken into account. The influence of the external magnetic field, detector efficiencies, scattering, and the geometrical acceptance, should be well understood. The parameters which can not be measured, are therefore determined from Monte Carlo simulations using GEANT4

Superfluidity of a perfect quantum crystal

In recent years, experimental data were published which point to the possibility of the existence of superfluidity in solid helium. To investigate this phenomenon theoretically we employ a hierarchy of equations for reduced density matrices which describes a quantum system that is in thermodynamic equilibrium below the Bose-Einstein condensation point, the hierarchy being obtained earlier by the author. It is shown that the hierarchy admits solutions relevant to a perfect crystal (immobile) in which there is a frictionless flow of atoms, which testifies to the possibility of superfluidity in ideal solids. The solutions are studied with the help of the bifurcation method and some their peculiarities are found out. Various physical aspects of the problem, among them experimental ones, are discussed as well.Comment: 24 pages with 2 figures, version accepted for publication in Eur.Phys.J.