Electromagnetic Corrections to Decay Amplitudes
We report on the status of our programme to develop a framework for the calculation of electromagnetic corrections to weak decay amplitudes. The $O(1\%)$ precision increasingly being reached in isospin-symmetric QCD calculations necessitates the inclusion of isospin-breaking effects, including electromagnetism, if continuing progress in the determination of the fundamental parameters of the Standard Model and the exploration of the limits of its validity is to be maintained. We briefly review the framework and the demonstration that for leptonic decays of pseudoscalar mesons the $O(1/L)$ finite-volume corrections ($L$ is the spacial extent of the box) are universal and have been calculated. We discuss the work-in-progress to extend the framework to semileptonic decays.
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Weak Decays and Matrix Elements