对罕见B介子半轻子衰变的色散研究
A Dispersive Look at Rare $B$-meson Semileptonic Decays
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中文总结 AI 辅助
研究罕见b→s味变中性流跃迁，通过色散矩阵法确定形状因子，考虑强子不确定性进行全局分析，结合最新测量给出新的标准模型预测及新物理分析。
中文摘要 AI 辅助
罕见的半轻子b→s味变中性流跃迁为标准模型提供了严格检验。其解释受强子不确定性限制，特别是B→K^(*)和B_s→ϕ形状因子及四夸克算符的矩阵元。我们充分考虑这些不确定性对b→sℓ^+ℓ^-跃迁进行全局分析，通过色散矩阵法确定形状因子，并比较仅基于格点QCD和还包括低q^2光锥求和规则输入的设置。与同时考虑两种输入的情况相比，仅使用格点QCD会大幅扩大大反冲时形状因子的不确定性。结合最新的LHCb和CMS对强相位敏感的角测量，我们的全局拟合为支持长程强子效应而非C_9中的短程偏移提供了更强证据。我们还给出了理论上干净的b→sνν模式的新的标准模型预测，其仅依赖于局域形状因子，并在弱有效理论中对这些跃迁进行了新物理分析，讨论了它们对近期 Belle II测量解释和现有实验上限的影响。
英文摘要
Rare semileptonic $b \to s$ flavour-changing neutral current transitions provide stringent tests of the Standard Model. Their interpretation is limited by hadronic uncertainties, notably the $B \to K^{(*)}$ and $B_s \to ϕ$ form factors (FFs) and the matrix elements of four-quark operators. We perform a global analysis of $b \to s \ell^+\ell^-$ transitions taking these uncertainties fully into account, determining the FFs through the Dispersive Matrix method and comparing a setup based solely on lattice QCD (LQCD) with one that also includes light-cone sum-rule (LCSR) inputs at low $q^2$. Compared to the case where both input are taken into account, using only LQCD substantially enlarges the FF uncertainties at large recoil. Combined with the latest LHCb and CMS angular measurements sensitive to strong phases, our global fit yields strengthened evidence in favour of long-distance hadronic effects rather than a short-distance shift in $C_9$. We further present new SM predictions for the theoretically clean $b \to s ν\barν$ modes, which depend only on local FFs, and a New Physics analysis of these transitions in the Weak Effective Theory, discussing their impact on the interpretation of the recent Belle~II measurement and on the available experimental upper bounds.
