在B介子b→u跃迁中寻找新物理：用 Belle II 数据重新审视
Hunting for new physics in $B$ meson $b \to u$ transitions: A fresh look with Belle II data
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中文总结 AI 辅助
利用Belle II数据对特定B介子衰变分析，采用广义低能哈密顿量，通过拟合分箱可观测量约束耦合参数空间，经全局拟合确定\(|V_{ub}|\)及新物理耦合，以此寻找新物理。
中文摘要 AI 辅助
我们利用 Belle II 合作组最近报告的半轻子模式下分箱微分分支比的精确测量，对\(B^- \to \ell^- {\bar \nu}_\ell\)、\(\bar B^0 \to \pi^+ \ell^- {\bar \nu}_\ell\)和\(B^- \to \rho^0 \ell^- {\bar \nu}_\ell\)衰变进行分析。采用广义低能哈密顿量，结合所有含左手轻子的六维算符，与标准模型有效场论一致，有依赖于轻子味的复威尔逊系数。对三个\(|V_{ub}|\)代表性值，拟合测量的\(q^2\)分箱可观测量以约束耦合参数空间并确定置信区域。最后对三个衰变通道进行全局拟合，确定\(|V_{ub}|\)及新物理耦合。
英文摘要
We present an analysis of the decays $B^- \to \ell^- {\bar ν}_\ell$, $\bar B^0 \to π^+ \ell^- {\bar ν}_\ell$, and $B^- \to ρ^0 \ell^- {\bar ν}_\ell$ leveraging the precise measurements of binned differential branching fractions recently reported by the Belle II Collaboration for the semileptonic modes. We adopt a generalized low-energy Hamiltonian that incorporates all dimension-six operators with left-handed neutrinos -- consistent with the Standard Model effective field theory (SMEFT) -- featuring complex, lepton-flavor-dependent Wilson coefficients. For three representative values of $|V_{ub}|$, we perform a fit to the measured $q^2$-binned observables to constrain the coupling parameter space and determine the corresponding confidence regions. Finally, we perform a global fit for the three decay channels, determining $|V_{ub}|$ together with the new physics couplings.
