The description of processes involving multi-body nonleptonic decays is very challenging. Data sets are very large nowadays, and demand better models.
In this work we focus on three-kaon weak matrix elements $\langle (KKK)^+|A_{\mu}|0\rangle$,
expressed as a relatively simple structure, which generalizes the concept of form factor.
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This is particularly important for $D^+ \to K^+ K^- K^+$ decay considering the dominance of annihilation weak topology. Here, we present the first version of a model to $D^+ \to K^+ K^- K^+$ decay which encompass naturally all final states topologies, including a proper multi-particle structures that cannot be decomposed into simpler two-body processes. All the structures are derived from a chiral effective theory and dressed with coupled channels where appropriate. The final amplitude contain only 3 free parameters related to $f_0(980)$ that are predicted by the theory but needs to be fine-tuned by a fit to data. This approach represents a significant improvement when compared to isobar
model, often employed in analyses of heavy-meson decay data.