在SMEFT中关联$B\to K^{(\ast)} ν\barν$与味异常
Correlating $B\to K^{(\ast)} ν\barν$ and flavor anomalies in SMEFT
AI总结：
本文在SMEFT框架下利用四个算子关联了$b\to sν\barν$等味改变中性流过程与其他味异常，通过全局拟合确定了Wilson系数范围，并成功预测了多个稀有衰变的分支比。
摘要：
Belle-II最近对$\mathcal{B}(B^+\to K^+ν\barν)$的测量结果显示出与标准模型（SM）预测存在$2.8~σ$的偏差。将此与先前Belle对$\mathcal{B}(B^{0}\to K^{\ast0}ν\barν)$的测量相结合，比值$\mathcal{B}(B^{0}\to K^{\ast0}ν\barν)/\mathcal{B}(B^+\to K^+ν\barν)$的上限明显小于SM预测。在本工作中，在标准模型有效场论（SMEFT）框架内解决了这些张力。由低能有效场论（LEFT）算子描述的味观测量，在电弱尺度上由SMEFT相互关联。利用仅四个SMEFT算子的集合，FCNC过程$b\to sν\barν$与$b\to s\ell^+\ell^-$、$b\to u_i\ell\barν$、$u_j\to s\ell\barν$、$u_j\to u_iν\barν$以及$u_j\to u_i\ell^+\ell^-$相关联。随后，我们通过一个容纳$R_{K^{(\ast)}}$、$R_{D^{(\ast)}}$和$\mathcal{B}(B\to K^{(\ast)}ν\barν)$等味异常的全局拟合，获得了这四个算子的最新Wilson系数范围。我们的发现表明，基于拟合的系数，对$\mathcal{B}(B^+\to τ^+ν_τ)$和$\mathcal{B}(D_s^+\to τ^+ν_τ)$的预测与Belle和BESIII的测量值非常吻合。预测的$B^0\to K^{\ast0}ν\barν$分支比为$(1.42\pm 0.74)\times 10^{-5}$，非常接近当前实验上限。预计在不久的将来，稀有衰变$B_s\to τ^+ τ^-$的分支比将达到$10^{-4}$量级。
英文摘要：
The recent measurement of $\mathcal{B}(B^+\to K^+ν\barν)$ by Belle-II reveals a $2.8~σ$ deviation from the Standard Model (SM) prediction. Combining this with a prior Belle measurement of $\mathcal{B}(B^{0}\to K^{\ast0}ν\barν)$, the upper bound of the ratio $\mathcal{B}(B^{0}\to K^{\ast0}ν\barν)/\mathcal{B}(B^+\to K^+ν\barν)$ is notably smaller than the SM prediction. In this work, tensions are solved within the framework of Standard Model Effective Field Theory (SMEFT). Flavor observables, described by Low-Energy Effective Field Theory (LEFT) operators, are interconnected by SMEFT at the electroweak scale. Utilizing a set of only four SMEFT operators, the FCNC process $b\to sν\barν$ is correlated with $b\to s\ell^+\ell^-$, $b\to u_i\ell\barν$, $u_j\to s\ell\barν$, $u_j\to u_iν\barν$, and $u_j\to u_i\ell^+\ell^-$. Subsequently, we obtain the latest ranges of Wilson coefficients for these four operators through a global fit that accommodates flavor anomalies such as $R_{K^{(\ast)}}$, $R_{D^{(\ast)}}$, and $\mathcal{B}(B\to K^{(\ast)}ν\barν)$. Our findings reveal that predictions for $\mathcal{B}(B^+\to τ^+ν_τ)$ and $\mathcal{B}(D_s^+\to τ^+ν_τ)$ align well with measured values from Belle and BESIII, based on the fitted coefficients. The predicted branching fraction for $B^0\to K^{\ast0}ν\barν$ is $(1.42\pm 0.74)\times 10^{-5}$, closely approaching the current experimental upper limit. Anticipation surrounds the rare decay $B_s\to τ^+ τ^-$, expected in the near future with a branching fraction on the order of $10^{-4}$.
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