Weak decays

The weak interactions have a particular interest because they have a very rich phenomenology, and these topics reveal a great deal of the fundamental theory. When writing our book, we became aware of how each separate reaction has its own literature and indeed forms its own little sub-field. It was impossible to describe each in the detail that it deserves, yet each contributes to the richness of our understanding of the Standard Model. Barry, Gene and I wrote Physics reports that describes these in more detail.

Let me just highlight a few papers that show the range of processes (and range of energies) that have been considered.

In kaon physics, the
Kl4 decay provides a highly non-trivial test of chiral perturbation theory, as well as a test of the large N approximation. This process has also been later used to provide constraints on the pi-pi scattering amplitudes. It is actually a powerful lab for the strong interactions.

In contrast, hyperon decays give us some of the key constraints on the weak mixing angles, i.e. the Cabibbo angle. Understanding SU(3) breaking is crucial for this effort.

Going to somewhat higher energies, using heavy quarks one can also probe interesting physics in rare B decays .

Finally, at the highest energies, the techniques developed for low energy processes can also be used to describe WW scattering.

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Research and teaching pages for John Donoghue