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

Abstract

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