Measurement of EPR-type flavour entanglement in U(4S) →

The neutral B-meson pair produced at the U(4S) should ex- hibit a non-local correlation of the type discussed by Einstein, Podol- ski, and Rosen. The time-dependent flavour asymmetry of the B mesons decaying into flavour eigenstates is used to test such a cor- relation. The asymmetry obtained from semileptonic B 0 decays is in agreement with the prediction from quantum mechanics and far away from the predictions of the local realistic models tested. The observation of partial decoherence in EPR systems could be a sig- nal for New Physics: we have tested for such effects, and found our results are consistent with no decoherence.