Loading...
Electroweak interactions and exchange currents in nuclei
Ananyan, Sergei M.
Ananyan, Sergei M.
Abstract
In the first part of the dissertation, a consistent model for the long-range part of the weak meson exchange currents (MEC) preserving basic symmetries of the strong interactions is developed within the framework of an hadronic field theory of nuclear structure (QHD). A model which builds the nucleon-nucleon interaction out of {dollar}\sigma,\ \omega{dollar} and {dollar}\pi{dollar} meson exchange is used to describe strong interactions in a nucleus. The scalar-pseudoscalar part of the problem coincides with the {dollar}\sigma{dollar}-model. In the linear realization of the sigma-model one obtains spatial axial exchange currents of order (1/M) in a non-relativistic decomposition in nucleon mass due to {dollar}\omega{dollar}-exchange. Consistency with the nuclear physics phenomenology requires the use of a very large {dollar}\rm m\sb{lcub}scalar{rcub},{dollar} and the low-mass {dollar}\sigma{dollar} cannot be introduced simply without breaking chiral invariance in this approach. A chiral transformation to the non-linear realization of the sigma-model is shown to be the natural way of treating the problem. PCAC is then satisfied identically for a one-body axial current even for a nucleon inside the nucleus. In this approach, the phenomenological low-mass {dollar}\sigma{dollar} can be incorporated in the model as a chiral singlet, still necessitating no additional exchange currents of order (1/M) to be present. Here the first appearance of the axial MEC is in the familiar {dollar}\pi{dollar}-exchange term of order {dollar}\rm (1/M\sp2){dollar} in the axial charge density. at the same time, there is now an additional relativistic one-body correction of order (1/M) in the spatial part of the weak axial current that is required to satisfy PCAC. These correction terms are included in a unified analysis of weak and electromagnetic processes with some selected light nuclei where transition densities have been previously determined from available electromagnetic data.;In the second part of the dissertation, a potential use of electroweak experiments with excited {dollar}(J\sp{lcub}\pi{rcub}T) = (0\sp+0){dollar} nuclear states in addition to the ground state with the same quantum numbers is discussed. Existing low momentum transfer {dollar}q\sp2{dollar} data on the inelastic charge form factor for the {dollar}\rm (0\sp+0)\sb{lcub}gnd{rcub}\to (0\sp+0)\sp{lcub}\*{rcub}{dollar} transition in {dollar}\rm\sp4He{dollar} are fit within simple nuclear models, and predictions are made for higher {dollar}q\sp2.{dollar}.
Description
Date
1996
Journal Title
Journal ISSN
Volume Title
Publisher
Collections
Download Dataset
Files
Loading...
9805156.pdf
Adobe PDF, 3.48 MB
Rights Holder
Usage License
Embargo
Research Projects
Organizational Units
Journal Issue
Keywords
Citation
Advisor
Department
Physics
DOI
https://dx.doi.org/doi:10.21220/s2-kj0q-5v63
Embedded videos
An error occurred retrieving the object's statistics