Strong CP and the Up Quark Mass Revisited

It is still a mystery why the strong interactions conserve CP to fantastic accuracy. Dynamical explanations have been proposed, but it is a curious fact that no model appears completely satisfactory. I will review the mechanisms and some of their puzzling features, highlighting opportunities for study and model-building. I will also revisit in detail the “vanishing up quark mass” solution, which is in sharp tension with lattice fits, and describe two approaches to cross-checking the lattice result.

Seminar slides