Physical Review D, vol.111, no.1, 2025 (SCI-Expanded)
In this study, we calculate the mixing angles between the axial-vector mesons D1(s1)-D1(s1)′ and B1(s1)-B1(s1)′ using the QCD sum rules approach. Our results are θ1=28.2±0.6°, θ2=26.6±0.6°, θ3=38.6±0.1°, and θ4=38.5±0.1°. These values are in good agreement with the predictions of heavy quark effective theory, particularly for the mixing angle θ=35.3°, and are compatible with several existing results in the literature. The predicted mixing angles can be tested through the analysis of semileptonic decays such as Bc→B1ℓν, Bc→Bs10ℓν, Bs→Ds1ℓν, and Bs→Ds1′ℓν, which can be investigated at experimental facilities such as LHCb and Belle II.