Rare B, D and K decays, radiative and electroweak penguin decays, including constraints on V_(td)/V_(ts) and ε'/ε: Summary of CKM 2018 working group 3

Rare $B$, $D$ and $K$ decays provide interesting probes of the Standard Model (SM), with a potential sensitivity to New Physics (NP) higher than other, more common, decays. Their experimental measurement is challenging, and their theoretical interpretation requires a precise knowledge of QCD at low energies, in the non-perturbative (hadronic) regime. The various $b$, $c$, $s$ decays provide different types of tests of the Standard Model, which can be performed in different experimental settings and which may exhibit correlated deviations in models of New Physics.