The important quantities of the B0d system, such as sin2β and Δmd, are determined under the assumption of perfect quantum coherence. However, any real system interacts with its environment and this interaction can lead to decoherence. It is therefore desirable to re-examine the procedures of determination of sin2β and Δmd in meson systems with decoherence. We find that the present values of these two quantities are modulated by the decoherence parameter λ. Re-analysis of B0d data from B-factories and LHCb can lead to a clean determination of λ, sin2β and Δmd. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).