另一个SMEFT故事：$Z^\prime$面临$\varepsilon'/\varepsilon$、$ΔM_K$和$K\toπν\barν$的新结果
Another SMEFT Story: $Z^\prime$ Facing New Results on $\varepsilon'/\varepsilon$, $ΔM_K$ and $K\toπν\barν$
摘要：
最近RBC-UKQCD晶格合作组提出了标准模型（SM）中与比率$\varepsilon'/\varepsilon$相关的强子矩阵元的新结果。随着威尔逊系数和同位旋破缺效应的现有知识，仍然有很大的空间，新的物理（NP）的贡献$\varepsilon'/\varepsilon$，既可以提高或抑制这个比率，以符合数据。另一方面，来自RBC-UKQCD的$K^0-\bar K^0$质量差$ΔM_K$的新SM值是$2σ$，高于抑制$ΔM_K$所需的NP的数据暗示。同时，来自NA 62的$K^+\rightarrowπ^+ν\barν$和来自KOTO的$K_{L}\rightarrowπ^0ν\barν$的最新结果仍然允许显著的NP贡献。我们指出，抑制$ΔM_K$的NP需要存在新的CP-违反相位与有趣的影响$K\toπν\barν$，$K_S\toμ^+μ^-$和$K_L\toπ^0\ell^+\ell^-$衰变。考虑到一个$Z^\prime$ -SMEFT内的情况下，我们分析了所有这些可观的依赖于NP的大小仍然允许的数据$\varepsilon'/\varepsilon$。$\varepsilon'/\varepsilon$的NP QCD企鹅情景被$\varepsilon_K$中的SMEFT重整化群效应所排除，因此$\varepsilon'/\varepsilon$中的NP效应由电弱企鹅支配。我们还调查了第一次是否存在一个重的$Z^\prime$违反味耦合可以产生通过顶部汤川重整化群效应FCNC介导的SM $Z$ -玻色子。结果证明是非常有趣的。
英文摘要：
Recently the RBC-UKQCD lattice collaboration presented new results for the hadronic matrix elements relevant for the ratio $\varepsilon'/\varepsilon$ in the Standard Model (SM). With the present knowledge of the Wilson coefficients and isospin breaking effects there is still much room for new physics (NP) contributions to $\varepsilon'/\varepsilon$ which could both enhance or suppress this ratio to agree with the data. The new SM value for the $K^0-\bar K^0$ mass difference $ΔM_K$ from RBC-UKQCD is on the other hand by $2σ$ above the data hinting for NP required to suppress $ΔM_K$. Simultaneously the most recent results for $K^+\rightarrowπ^+ν\barν$ from NA62 and for $K_{L}\rightarrowπ^0ν\barν$ from KOTO still allow for significant NP contributions. We point out that the suppression of $ΔM_K$ by NP requires the presence of new CP-violating phases with interesting implications for $K\toπν\barν$, $K_S\toμ^+μ^-$ and $K_L\toπ^0\ell^+\ell^-$ decays. Considering a $Z^\prime$-scenario within the SMEFT we analyze the dependence of all these observables on the size of NP still allowed by the data on $\varepsilon'/\varepsilon$. The NP QCD penguin scenario for $\varepsilon'/\varepsilon$ is excluded by SMEFT renormalization group effects in $\varepsilon_K$ so that NP effects in $\varepsilon'/\varepsilon$ are governed by electroweak penguins. We also investigate for the first time whether the presence of a heavy $Z^\prime$ with flavour violating couplings could generate through top Yukawa renormalization group effects FCNCs mediated by the SM $Z$-boson. The outcome turns out to be very interesting.
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