Exploring CP violation and η–η′ mixing with the B0s,d → J/ψη(′) systems

The B0s,d → J/ψη(′) decays provide new terrain for exploring CP violation. After briefly discussing η–η ′ mixing, we analyse the effective lifetimes and CP-violating observables of the Bs channels, which allow us to probe New-Physics effects in B 0 s– B̄0s mixing. We have a critical look at these observables and show how hadronic corrections can be controlled by means of the Bd decays. Using measurements of the B0s,d → J/ψη(′) branching ratios by the Belle collaboration, we discuss tests of the SU(3)F flavour symmetry of strong interactions, obtain the first constraints on the hadronic parameters entering the B0s,d → J/ψη system, and predict the B0d → J/ψη ′ branching ratio at the 5 × 10−6 level. Furthermore, we present strategies for the determination of the η–η ′ mixing parameters from the B0s,d → J/ψη(′) observables. We also observe that the B0s,d → J/ψη and B0s,d → J/ψη ′ decays are – from a formal point of view – analogous to the quark–antiquark and tetraquark descriptions of the f0(980) in the B 0 s,d → J/ψf0(980) channels, respectively