Weak and Electromagnetic Radiative Corrections in Atomic Physics

自20世纪40年代末量子电动力学（QED）最初的成功以来，辐射修正在理论物理学的发展中起着中心作用。由于束缚态电子传播子的复杂性，它们在原子和离子中的计算在技术上具有挑战性。两个理论工具将用于这个项目来解决这个问题。第一种是S-矩阵理论，它最适用于高电荷态离子。量子电动力学效应在这些离子中得到了很大的增强，最近的实验进展为这一物理提供了丰富的敏感数据，S矩阵理论可以用来系统地计算这些离子中的辐射修正，提供对量子电动力学的检验，并可能通过理论与实验的比较发现新的物理。展开参数1/Z的存在使处理有限的费曼图变得简单。这一工作的一个主要部分是计算这些图，这应该允许上述测试。在中性原子中，1/Z展开参数是不可用的，精确测试要困难得多。非相对论QED（NRQED）近年来的一个主要发展是在少电子系统中的应用。这种技术允许一个开始与薛定谔方程，它可以解决高精度的丧失电子原子。NRQED提供了一个系统的方法来解释相对论和QED修正。本文的另一个重要组成部分是将这种方法应用于氦原子的精细结构，通过与已有实验的比较，可以高精度地确定精细结构常数.最后，本文还提出了对重中性原子宇称不守恒（PNC）过程的辐射修正的估算.最早的粒子物理评估这种辐射校正，其中涉及自由传播，显着改变时，绑定传播使用。一个完整的计算尚未进行，但在以前的资助下进行的工作应该是概括到这个复杂的任务，这具有重要的粒子物理意义。

Radiative corrections have played a central role in the development of theoreticalphysics since the original successes of Quantum Electrodynamics (QED) in the late1940's. Their calculation in atoms and ions is technically challenging because of thecomplexity of the electron propagator in bound states. Two theoretical tools willbe used in this project to attack this problem. The first, S-matrix theory, is mostapplicable 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 theseions, provide tests of QED, and possibly uncover new physics through the comparisonof theory and experiment. The existence of an expansion parameter, 1/Z, leads tothe simplification of having to deal with a limited set of Feynman diagrams. A majorpart of this work involves the calculation of these diagrams, which should allowthe above-mentioned tests.In neutral atoms the 1/Z expansion parameter is not available, and precision testsare much more difficult. A major development of recent years has been the applicationof non-relativistic QED (NRQED) to few-electron systems. This technique allows oneto start with the Schroedinger equation, which can be solved with high accuracy forfew-electron atoms. NRQED provides a systematic method to account for relativisticand QED corrections. Another major component of the proposed research is applica-tion of this method to the fine structure of helium, where comparison of sufficientlyadvanced theory with already existent experiments should allow a determination ofthe 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 evaluationsof this radiative correction, which involved free propagators, are significantly changedwhen 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 complextask, which has important particle physics implications.