On the ultimate precision of meson mixing observables

Meson mixing is considered to be an ideal testing ground for new physics searches. Experimental precision has greatly increased over the recent years, exceeding in several cases the theoretical precision. A possible limit in the theoretical accuracy could be a hypothetical breakdown of quark-hadron duality. We propose a simple model for duality violations and give stringent phenomenological bounds on its effects on mixing observables, indicating regions where future measurements of ΔΓd, asld and asls would give clear signals of new physics. Finally, we turn our attention to the charm sector, and reveal that a modest duality violation of about 20% could explain the huge difference between HQE predictions for D mixing and experimental data.