Speaker
Payton Arber
(The George Washington University)
Description
When a meson decay violates isospin symmetry, it often signals electromagnetic or weak effects, since the strong interaction approximately conserves isospin. The decays $η→π^+π^−π^0$ and $η→3π^0$, however, are an important exception: they are hadronic decays driven primarily by strong isospin breaking from the up-down quark mass difference. Because the leading electromagnetic contribution is suppressed, η→3π provides a uniquely clean window into $m_d-m_u$ and the light-quark mass ratio Q. This talk discusses why the decay is forbidden in the exact isospin limit, how the Standard Model quark-mass term makes it possible, and how branching fractions and Dalitz plot distributions connect experimental measurements to low-energy QCD.
Author
Payton Arber
(The George Washington University)