Parametrizations of three-body hadronic $B$- and $D$-decay amplitudes

International audienceA short review of our recent work on amplitude parametrizations of three-body hadronic weak B and D decays is presented. The final states are here composed of three light mesons, namely the various charge πππ, Kππ and KK states. These parametrizations are derived from previous calculations based on a quasi-two-body factorization approach where the two-body hadronic final state interactions are fully taken into account in terms of unitary S- and P-wave ππ, πK and K form factors. They are an alternative to the isobar-model description and can be useful in the interpretation of CP asymmetries