Local realistic theories and quantum mechanics for the two-neutral-kaon system Original Research Article

The predictions of local realistic theories for the observables concerning the evolution of a K0K̄ 0 quantum entangled pair (created in the decay of the φ-meson) are discussed. It is shown, in agreement with Bellʹs theorem, that the most general local hidden-variable model fails in reproducing the whole set of quantum-mechanical joint probabilities. We achieve these conclusion by employing two different approaches. In the first approach, the local realistic observables are deduced from the most general premises concerning locality and realism, and Bell-like inequalities are not employed. The other approach makes use of Bellʹs inequalities. In the first approach, under particular conditions for the detection times, the discrepancy between quantum mechanics and local realism for the time-dependent asymmetry turns out to be not less than 20%. A similar incompatibility can be made evident by means of a Bell-type test by employing both Wignerʹs and (once properly normalized probabilities are used) Clauser–Horne–Shimony–Holtʹs inequalities. Because of its relatively low experimental accuracy, the data obtained by the CPLEAR collaboration for the asymmetry parameter do not yet allow a decisive test of local realism. Such a test, both with and without the use of Bellʹs inequalities, should be feasible in the future at the Frascati Φ-factory.