Probing new physics in class-I B-meson decays into heavy-light final states

A bstract With updated experimental data and improved theoretical calculations, several significant deviations are being observed between the Standard Model predictions and the experimental measurements of the branching ratios of B ¯ s 0 → D s ∗ + L − decays, where L is a light meson from the set { π , ρ , K (∗) }. Especially for the two channels B ¯ 0 → D + K − and B ¯ s 0 → D s + π − , both of which are free of the weak annihilation contribution, the deviations observed can even reach 4–5 σ . Here we exploit possible new-physics effects in these class-I non-leptonic B -meson decays within the framework of QCD factorization. Firstly, we perform a model-independent analysis of the effects from twenty linearly independent four-quark operators that can contribute, either directly or through operator mixing, to the quark-level b → c u ¯ d s transitions. It is found that, under the combined constraints from the current experimental data, the deviations observed could be well explained at the 1 σ level by the new-physics four-quark operators with γ μ (1 − γ 5 ) ⨂ γ μ (1 − γ 5 ) structure, and also at the 2 σ level by the operators with (1 + γ 5 ) ⨂ (1 − γ 5 ) and (1 + γ 5 ) ⨂ (1 + γ 5 ) structures. However, the new-physics four-quark operators with other Dirac structures fail to provide a consistent interpretation, even at the 2 σ level. Then, as two specific examples of model-dependent considerations, we discuss the case where the new-physics four-quark operators are generated by either a colorless charged gauge boson or a colorless charged scalar, with their masses fixed both at the 1 TeV. Constraints on the effective coefficients describing the couplings of these mediators to the relevant quarks are obtained by fitting to the current experimental data.