Branching Fractions and CP-Violating Asymmetries in D => PP Decays

Abstract

We update an $SU(3)_F$ analysis of $D\to PP$ decays ($P\equiv π, K$) in which the dominant $SU(3)_F$-breaking effects are modeled through final-state interactions. The new fit improves the description relative to the previous parameter set, although significant global tension remains, mainly in charged-$D$ modes. Within the adopted rescattering model, the direct CP asymmetries in $D^0\toπ^+π^-$, $K^+K^-$, $π^0π^0$, and $K_S^0 K_S^0$ depend on two additional reduced amplitudes. Using the $D^0\toπ^+π^-$ and $D^0\to K^+K^-$ asymmetries as inputs, we derive conditional predictions for the two neutral modes. The OZI-motivated benchmark $Δ_4=0$ is mildly disfavored by the charged-mode asymmetries and leads to substantially smaller asymmetries in the neutral modes, which can be tested with more precise $K_S^0K_S^0$ and $π^0π^0$ measurements.