Radiative three-body D-meson decays in and beyond the standard model

Abstract We study radiative charm decays $$D \rightarrow P_1 P_2 \gamma $$ D → P 1 2 γ , $$P_{1,2}=\pi ,K$$ , = π K in QCD factorization at leading order and within heavy hadron chiral perturbation theory. Branching ratios including resonance contributions are around $$\sim 10^{-3}$$ ∼ 10 - 3 for the Cabibbo-favored modes into $$K \pi 10^{-5}$$ 5 singly Cabibbo-suppressed $$\pi ^+ ^- K^+ K^- + thus reach of flavor factories BES III Belle II. Dalitz plots forward–backward asymmetries reveal significant differences between two frameworks; such observables therefore ideally suited a data-driven identification relevant decay mechanisms standard-model dominated K decays. This increases potential to probe new physics with decays, which sensitive enhanced dipole operators. CP useful test SM look neutral $$|\Delta C|=1$$ | Δ C transitions. Cuts plot enhance sensitivity due presence both s - t u -channel intermediate resonances.