Anomalous Magnetic Moment of The Electron
The one-loop contribution to the anomalous magnetic moment—corresponding to the first and largest quantum mechanical correction—of the electron is found by calculating the vertex function shown in the diagram on the right. The calculation is relatively straightforward and the one-loop result is:
where is the fine structure constant. This result was first found by Schwinger in 1948. As of 2009, the coefficients of the QED formula for the anomalous magnetic moment of the electron have been calculated through order, and are known analytically up to . The QED prediction agrees with the experimentally measured value to more than 10 significant figures, making the magnetic moment of the electron the most accurately verified prediction in the history of physics. (See precision tests of QED for details.)
The current experimental value and uncertainty is:
According to this value, a is known to an accuracy of around 1 part in 1 billion (109). This required measuring g to an accuracy of around 1 part in 1 trillion (1012).
Read more about this topic: Anomalous Magnetic Dipole Moment
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