I will present a multi-meson model applied to the specific case of three-kaon weak matrix elements. We propose a model for the decay D+ -> K+K−K+ as an alternative to isobar model, with free parameter predicted by the theory to be fine-tuned by a fit to data. An important qualitative outcome is that we encompass naturally all final states topologies, which involve necessarily proper multi-particle structures and cannot be decomposed into simpler two-body processes.
Inspired in this model, we developed a new phenomenological model suited to all SU(3) mesonic two-body final-state interactions up to energies around 2 GeV to replace the isobar model.
We show that the new model provides a clear indication of the mechanism responsible for the sharp rise observed in the ππ phase around 1 GeV.
The phenomenological amplitudes proposed are suited to any number of resonances, incorporate chiral symmetry at low energies, include coupled channels, and respect unitarity.
References:
Phys. Rev. D 98 (2018) no.5, 056021. [arXiv:1805.11764]
Phys. Rev. D 102 (2020), 076012 . [arXiv:2007.12304]