We formulate a set of Bell's inequalities for the system of two correlated neutral kaons coming from the decay of a φ-meson, without assuming CP and CP T invariance. We show that a non-vanishing value of the phenomenological parameter ε ′ would violate such inequalities, ruling out Bell's locality.

Since the 1964 discovery of KL → π+π− [1], understanding CP violation has been a major goal of particle physics. Subsequent experiments showed that the dominant mechanism of CP violation in neutral kaons (still the only particle system in which CP violation has been observed) is a small asymmetry between K0 → K and K → K0 mixing. This asymmetry, referred to as indirect CP violation, results in ...