Rare K and B decays – almost perfect laboratories
If a meson lives long enough, it has a chance to show us many interesting phenomena. With ordinary transitions slowed down, quantum effects due to virtual intermediate states become relevant, and those can involve dynamical entities beyond the SM operating at much higher energy scales than MK or MB. Search for new phenomena where uninteresting ordinary decays are suppressed has yielded many hints in the past, and we can expect it to do so again in the future.
A voluminous tool chest has been created over the years. This field was pioneered by Gaillard and Lee ; the renormalization group analysis including penguins was introduced by Shifman, Vainshtein, Voloshin and Zakharov ; Gilman ...