发表机构
Institute of Particle and Nuclear Physics, Henan Normal University; Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University（河南师范大学粒子与核物理研究所; 华中师范大学粒子物理及夸克轻子物理教育部重点实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对B介子衰变分支比偏差，研究IV型标量双夸克解释，通过NLO匹配和QCD因子化计算，发现纯左手耦合能更好调和数据，并给出可检验预言。
AI 中文摘要
受 $\bar{B}_{(s)}^{0} \to D_{(s)}^{(*)+}L^-$（其中 $L=\pi,K^{(*)},\rho$）衰变分支比的实验数据与标准模型预言之间存在偏差的启发，我们研究了 IV 型标量双夸克能否为这些偏差提供合理解释。通过将完整理论中的重整化振幅匹配到用双夸克算子基表示的低能有效理论中的振幅，我们在新物理能标 $\mu_\phi=M_{\phi}$ 处提取了相应的 Wilson 系数，计算精度达到 $\alpha_s$ 的次领头阶（NLO）。随后，我们将所得算子改写为标准模型基，并利用重整化群演化将 Wilson 系数降至强子能标 $\mu_b=m_b$。对于相关新物理算子的强子矩阵元，我们采用 QCD 因子化方法计算不可因子化的单圈顶点修正，并将理论预言与最新实验数据对比，以约束双夸克参数空间。在单耦合情形下，我们发现纯左手耦合 $\Delta_{d(s)}^{LL}$ 能在 $1\sigma$ 内调和这些偏差，而混合的右-左耦合 $\Delta_{d(s)}^{RL}$ 仅在约 $2\sigma$ 内与数据相容。扩展到双耦合情形时，我们发现只要 $\Delta_{d(s)}^{LL}\neq 0$ 就存在可行的参数区域。纳入 LHCb 对比值 $R_{\pi/\mu\nu_{\mu}}$ 的测量进一步缩小了 $\Delta_{d}^{LL}$ 的允许范围，但对 $\Delta_{d}^{RL}$ 未产生有意义的额外限制。因此，尽管 $\Delta_{d(s)}^{LL}$ 或 $\Delta_{d(s)}^{RL}$ 各自都能单独提供可接受的新物理解释，但我们的唯象结果倾向于由纯左手双夸克-夸克耦合主导的情形。最后，我们给出了分支比和比值 $R_{(s)L}^{(*)}$ 的更新预言，这些预言可由即将进行的 LHCb 和 Belle II 实验检验。
英文摘要
Motivated by the deviations between experimental data and SM predictions for the branching fractions of $\bar{B}_{(s)}^{0} \to D_{(s)}^{(*)+}L^-$ decays with $L=π,K^{(*)},ρ$, we investigate whether the type-IV scalar diquark can offer a plausible explanation for them. By matching the renormalized amplitudes in the full theory onto those in the low-energy effective theory formulated in the diquark operator basis, we extract the corresponding Wilson coefficients up to NLO in $α_s$ at the NP scale $μ_ϕ=M_ϕ$. We then rewrite the obtained operators in the SM basis and apply the renormalization-group running to evolve the Wilson coefficients down to the hadronic scale $μ_b=m_b$. For the hadronic matrix elements of the relevant NP operators, we employ the QCD factorization approach to evaluate the non-factorizable one-loop vertex corrections, and confront our theoretical predictions to the latest data to constrain the diquark parameter space. In the single-coupling case, we find that the purely left-handed coupling $Δ_{d(s)}^{LL}$ can reconcile the discrepancies at $1σ$, while the mixed right-left coupling $Δ_{d(s)}^{RL}$ remains compatible with data only at about $2σ$. Extending to the two-coupling case, we find viable parameter regions as long as $Δ_{d(s)}^{LL}\neq 0$. Incorporating the LHCb measurement of the ratio $R_{π/μν_μ}$ further reduces the allowed range of $Δ_{d}^{LL}$, but does not yield meaningful extra restriction on $Δ_{d}^{RL}$. Hence, while either $Δ_{d(s)}^{LL}$ or $Δ_{d(s)}^{RL}$ can separately provide an acceptable NP interpretation, our phenomenological results favor a scenario dominated by purely left-handed diquark-quark couplings. Finally, we present updated predictions for the branching fractions and the ratios $R_{(s)L}^{(*)}$, which can be probed by forthcoming LHCb and Belle II measurements.
Comments44 pages, 7 tables, 17 figures
