Gauge-fermion theories and their IR fate remain puzzling mysteries in QFT, even after decades of study. Beyond their theoretical interest, they may play a natural role in extensions of the Standard Model, such as grand unified theories, dynamical symmetry breaking, and models of quark and lepton substructure. Yet our limited understanding of their nonperturbative dynamics severely hampers...
We compute hadronic vacuum polarization, an observable whose precision limits several important tests of the Standard Model, using two-flavor chiral perturbation theory to three loops (next-to-next-to-next-to-leading order). Particular attention is given to the loop integrals, several of which are not found in literature, and which display a novel set of relations beyond what is found through...