Usamos o formalismo de A. Toledo Pisa e E. Passos, que usa o método de coordenadas geradores e o Teorema Espectral de Anélise Funcional, para obter uma hamiltoniana coletiva para as vibrações monopolares isoescalares nos núcleos duplamente mágicos ANPOT. 4 He, ANPOT. 16 O e ANPOT 40 C. As funções de onda do oscilador hermônico são tomadas como funções de onda geradoras, e a interação de muitos corpos é aquela de Skyrme. Com esta hamiltoniana coletiva calculamos o espectro de energias do modo monopolar isoescalar, parâmetros de inércia e módulos de incompressibilidade para aqueles núcleos e comparamos com os resultados de Flocard e Vautherin, que resolvem numericamente a equação de Griffin-Wheeler. Foram calculados ainda os raios quadráticos médios nucleares. Os efeitos espúrios dos movimentos do centro de massa são eliminados exatamente para o AMPOT. 4 He e recalculamos aquelas propriedades nucleares. / The isoscalar monopole vibrational mode in 4 He,16 O and 40Ca is studied with the aid of collective Hamiltonians obtained from e general formalism proposed by A. Toledo Piza and E. Passos, which makes use of the generator coordinate method and Functional Analisis Spectral Theorem. Cur generator wave functions are that of the harmonic oscillator and use is made of the Skyrme\'s schematic effective interaction. Using the collective Hamiltonian we can calculate the energy spectrum, inertial parameters end incompressibility modulus and compare with numerical results of Flocard and Vautherin. R. m. s. radii are also calculated. Center of mass spurious effects are exactly eliminated and the forementioned nuclear properties are calculated again for 4 He.

Applicability of the Hartree-Fock (HF) based random phase approximation (RPA) with several Skyrme effective interactions to the description of the isoscalar giant monopole (ISGMR) and the isoscalar giant dipole resonance (ISGDR) in 90Zr, 116Sn, 144Sm and 208Pb nuclei has been investigated. The existing Skyrme interactions SL1, SkM*, SGII, Sly4 and Sk255 were used. Hartree-Fock description of the ground state properties of all nuclei of interest was obtained using these Skyrme interactions. Transition strength distributions for the ISGMR and the ISGDR in nuclei of interest were calculated using coordinate space representation for the RPA in the Green’s function formalism with discretized continuum. A method of projecting out the spurious state contribution from the transition strength distribution and the transition density of the ISGDR was employed to eliminate spurious state mixing, due to a not fully selfconsistent description of the particle-hole interaction within the RPA. Differential cross sections of 240 MeV alpha-particles inelastic scattering on all nuclei of interest were calculated using the folding model within the distorted wave Born approximation (DWBA). Optical potentials were obtained by folding HF ground state densities with a alpha-nucleon density dependent Gaussian interaction. Parameters of the interaction were obtained by fitting experimental angular distribution of alpha-nucleus elastic scattering. The inelastic differential cross sections were calculated using both collective and microscopic transition densities. Possible underestimations of the energy weighted sum rule for the case of the ISGDR are reported. An alternative description for the ISGDR in nuclei based on the Fermi liquid drop model (FLDM) with the collisional Fermi surface distortion was investigated. The FLDM dispersion relation was obtained from the linearized Landau-Vlasov equation. Centroid energies, E0 and E1, and widths, gamma-0 and gamma-1, of the ISGMR and ISGDR, respectively, were calculated as functions of the damping parameter using appropriate boundary conditions. Comparison of the theoretical ratios of the ISGDR and ISGMR centroid energies, E1/E0, to the experimental values resulted in a damping parameter equal to 0.5, however, systematic overestimation of energy of the ISGMR and ISGDR by 2.0-2.5 MeV was observed. The applicability of the HF-RPA to the description for the ISGDR in nuclei is confirmed.

Usamos o formalismo de A. Toledo Pisa e E. Passos, que usa o método de coordenadas geradores e o Teorema Espectral de Anélise Funcional, para obter uma hamiltoniana coletiva para as vibrações monopolares isoescalares nos núcleos duplamente mágicos ANPOT. 4 He, ANPOT. 16 O e ANPOT 40 C. As funções de onda do oscilador hermônico são tomadas como funções de onda geradoras, e a interação de muitos corpos é aquela de Skyrme. Com esta hamiltoniana coletiva calculamos o espectro de energias do modo monopolar isoescalar, parâmetros de inércia e módulos de incompressibilidade para aqueles núcleos e comparamos com os resultados de Flocard e Vautherin, que resolvem numericamente a equação de Griffin-Wheeler. Foram calculados ainda os raios quadráticos médios nucleares. Os efeitos espúrios dos movimentos do centro de massa são eliminados exatamente para o AMPOT. 4 He e recalculamos aquelas propriedades nucleares. / The isoscalar monopole vibrational mode in 4 He,16 O and 40Ca is studied with the aid of collective Hamiltonians obtained from e general formalism proposed by A. Toledo Piza and E. Passos, which makes use of the generator coordinate method and Functional Analisis Spectral Theorem. Cur generator wave functions are that of the harmonic oscillator and use is made of the Skyrme\'s schematic effective interaction. Using the collective Hamiltonian we can calculate the energy spectrum, inertial parameters end incompressibility modulus and compare with numerical results of Flocard and Vautherin. R. m. s. radii are also calculated. Center of mass spurious effects are exactly eliminated and the forementioned nuclear properties are calculated again for 4 He.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23699号 / 理博第4789号 / 新制||理||1686(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 准教授 銭廣 十三, 教授 中家 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The role of scalar mesons in radiative vector meson decays is investigated. The effects of scalar-isoscalar f_{0}(980) and scalar-isovector a_{0}(980) mesons are studied in the mechanism of the radiative Phi-&gt / pi{+}pi{-}gamma and phi-&gt / pi{0}eta gamma decays, respectively. A phenomenological approach is used to study the radiative phi-&gt / pi{+}p{-}gamma decay by considering the contributions of sigma-meson, rho-meson and f_{0}-meson. The interference effects between different contributions are analyzed and the branching ratio for this decay is calculated. The radiative phi-&gt / pi{0}eta gamma decay is studied within the framework of a phenomenological approach in which the contributions of rho-meson, chiral loop and a_{0}-meson are considered. The interference effects between different contributions are examined and the coupling constants g_{phi a_{0} gamma} and g_{a_{0}K{+}K{-}} are estimated using the experimental branching ratio for the phi-&gt / pi{0}eta gamma decay. Furthermore, the radiative rho{0}pi{+}pi{-}gamma$ and rho{0}-&gt / pi{0}pi{0}gamma decays are studied to investigate the role of scalar-isoscalar sigma-meson. The branching ratios of the rho{0}-&gt / pi{+}pi{-}gamma and rho{0}-&gt / pi{0}pi{0}gamma decays are calculated using a phenomenological approach by adding to the amplitude calculated within the framework of chiral perturbation theory and vector meson dominance the amplitude of sigma-meson intermediate state. In all the decays studied the scalar meson intermediate states make important contributions to the overall amplitude.