Bargmann invariants and correlated geometric $$\mathcal CP$$ -violating structures in neutral meson systems

Abstract Bargmann invariants provide a rephasing-invariant description of phase relations among quantum states and offer a geometric perspective on interference phenomena. In this work, we investigate their role in neutral meson systems by constructing cyclic products involving the heavy and light mass eigenstates together with decay-projected states arising from correlated meson decays. Explicit expressions for third-order and fourth-order invariants are obtained in terms of mixing parameters and decay amplitudes. The analysis shows that the associated geometric phases encode $$\mathcal CP$$ C P -sensitive interference effects between meson–antimeson mixing and decay amplitudes and become trivial in the $$\mathcal CP$$ C P -conserving limit. Expressing the decay amplitudes in terms of CKM matrix elements reveals quartic combinations with analogous rephasing-invariant weak-phase structure to that of the Jarlskog invariant. We further introduce a rephasing-invariant ratio constructed from third- and fourth-order Bargmann invariants, which isolates correlated $$\mathcal CP$$ C P -violating structures that cannot, in general, be factorized into independent decay-channel contributions and can enhance sensitivity to small deviations from $$\mathcal CP$$ C P symmetry. The invariants can also be related to parameters governing time-dependent $$\mathcal CP$$ C P asymmetries in neutral meson decays, thereby providing a geometric interpretation of observable $$\mathcal CP$$ C P -violating interference effects.