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

<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>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 <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {\overline{B}}_{(s)}^0\to {D}_{(s)}^{\left(\ast \right)+}{L}^{-} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mover> <mml:mi>B</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mfenced> <mml:mi>s</mml:mi> </mml:mfenced> <mml:mn>0</mml:mn> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>D</mml:mi> <mml:mfenced> <mml:mi>s</mml:mi> </mml:mfenced> <mml:mrow> <mml:mfenced> <mml:mo>∗</mml:mo> </mml:mfenced> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> <mml:msup> <mml:mi>L</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> decays, where <jats:italic>L</jats:italic> is a light meson from the set {<jats:italic>π</jats:italic>, <jats:italic>ρ</jats:italic>, <jats:italic>K</jats:italic><jats:sup>(∗)</jats:sup>}. Especially for the two channels <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {\overline{B}}^0\to {D}^{+}{K}^{-} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mover> <mml:mi>B</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>D</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$ {\overline{B}}_s^0\to {D}_s^{+}{\pi}^{-} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mover> <mml:mi>B</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>s</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>D</mml:mi> <mml:mi>s</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula>, both of which are free of the weak annihilation contribution, the deviations observed can even reach 4–5<jats:italic>σ</jats:italic>. Here we exploit possible new-physics effects in these class-I non-leptonic <jats:italic>B</jats:italic>-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 <jats:italic>b →</jats:italic><jats:inline-formula><jats:alternatives><jats:tex-math>$$ c\overline{u}d(s) $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>c</mml:mi> <mml:mover> <mml:mi>u</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>d</mml:mi> <mml:mfenced> <mml:mi>s</mml:mi> </mml:mfenced> </mml:math></jats:alternatives></jats:inline-formula> transitions. It is found that, under the combined constraints from the current experimental data, the deviations observed could be well explained at the 1<jats:italic>σ</jats:italic> level by the new-physics four-quark operators with <jats:italic>γ</jats:italic><jats:sup><jats:italic>μ</jats:italic></jats:sup>(1 <jats:italic>− γ</jats:italic><jats:sub>5</jats:sub>) ⨂ <jats:italic>γ</jats:italic><jats:sub><jats:italic>μ</jats:italic></jats:sub>(1 <jats:italic>− γ</jats:italic><jats:sub>5</jats:sub>) structure, and also at the 2<jats:italic>σ</jats:italic> level by the operators with (1 + <jats:italic>γ</jats:italic><jats:sub>5</jats:sub>) ⨂ (1 <jats:italic>− γ</jats:italic><jats:sub>5</jats:sub>) and (1 + <jats:italic>γ</jats:italic><jats:sub>5</jats:sub>) ⨂ (1 + <jats:italic>γ</jats:italic><jats:sub>5</jats:sub>) structures. However, the new-physics four-quark operators with other Dirac structures fail to provide a consistent interpretation, even at the 2<jats:italic>σ</jats:italic> 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.</jats:p>