Weak and Electromagnetic Radiative Corrections in Atomic Physics

University Of Notre Dame, Notre Dame IN

Investigators

Abstract

Radiative corrections have played a central role in the development of theoretical physics since the original successes of Quantum Electrodynamics (QED) in the late 1940's. Their calculation in atoms and ions is technically challenging because of the complexity of the electron propagator in bound states. Two theoretical tools will be used in this project to attack this problem. The first, S-matrix theory, is most applicable to highly charged ions. QED effects are highly enhanced in these ions, and recent advances in experiment provide a wealth of data sensitive to this physics. S-matrix theory can be used to systematically calculate radiative corrections in these ions, provide tests of QED, and possibly uncover new physics through the comparison of theory and experiment. The existence of an expansion parameter, 1/Z, leads to the simplification of having to deal with a limited set of Feynman diagrams. A major part of this work involves the calculation of these diagrams, which should allow the above-mentioned tests. In neutral atoms the 1/Z expansion parameter is not available, and precision tests are much more difficult. A major development of recent years has been the application of non-relativistic QED (NRQED) to few-electron systems. This technique allows one to start with the Schroedinger equation, which can be solved with high accuracy for few-electron atoms. NRQED provides a systematic method to account for relativistic and QED corrections. Another major component of the proposed research is applica- tion of this method to the fine structure of helium, where comparison of sufficiently advanced theory with already existent experiments should allow a determination of the fine structure constant with high accuracy. Finally, the evaluation of radiative corrections to parity nonconserving (PNC) processes in heavy neutral atoms is proposed. The earliest particle physics evaluations of this radiative correction, which involved free propagators, are significantly changed when bound propagators are used. A full calculation has not yet been carried out, but work carried out under the previous grant should be generalizable to this complex task, which has important particle physics implications.