THE ISOBALIC ANALOG RESONANCE AND ISOSPIN SYMMETRY IN NUCLEI
Gianluca Colo
Dipartmento di Fisica Università degli Studi Via Celoria 16 20133 Milano (Italia)
日時：2000年07月26日（水） 15:00-
場所：サイクロトロンラジオアイソトープセンター会議室
The isobaric analog resonance (IAR) is intimately related to the (approximate) isospin symmetry in atomic nuclei. Recently, problems related to this symmetry and its breaking are discussed with new emphasis since the radioactive beams facilities can provide access to nuclei close to the drip lines, that is, with large isospin deformations. In this seminar, we plan to discuss the application to the IAR of a fully consistent microscopic model which is based on Hartree-Fock plus RPA and includes the coupling with two particle-two hole-type (2p2h) configurations and with the continuum. It will be shown that the model is able to provide a precise quantitative agreement with the experimental data for the energy, the width and the particle decay branching ratios of the IAR in 208Bi. In addition to the Coulomb force, the effect of other isospin-breaking forces of nuclear type turns out to be important. The relation between this and previous calculations of the IAR width will be discussed. Finally, we elucidate the relationship between the IAR width at finite temperature and the isospin symmetry restoration.