Soft-photon corrections in multi-body meson decays

The effects due to soft-photon emission (and the related virtual corrections) in multibody decays of B, D, and K mesons are analysed. We present analytic expressions for the universal O(α) correction factors which can be applied to all multi-body decay modes where a tight soft-photon energy cut in the decaying-particle rest-frame is applied. All-order resummations valid in the limit of small and large velocities of the final-state particles are also discussed. The phenomenological implications of these correction factors in the distortion of Dalitz-plot distributions of K → 3π decays are briefly analysed.