$K \to (ππ)_{I=2}$衰变振幅$A_2$的晶格测定
Lattice determination of the $K \to (ππ)_{I=2}$ Decay Amplitude $A_2$
摘要：
本文计算了K介子衰变为两个同位旋I = 2的π介子的振幅A_2。结果在信中物理. 108（2012）141601从63种胶子组态的分析中更新到146种组态，给出Re $A_2=1.381(46)_{\textrm{stat}}(258)_{\textrm{syst}} 10^{-8}$ GeV和Im $A_2=-6.54(46)_{\textrm{stat}}(120)_{\textrm{syst}}10^{-13}$ GeV。Re $A_2$与实验结果吻合良好，而Im $A_2$的值迄今为止是未知的。我们也在努力直接计算$K\to(ππ)_{I=0}$振幅$A_0$，但在标准模型中，我们的结果为Im $A_2$可以结合Re $A_0$，Re $A_2$和$ε^\prime/ε$的实验结果，得到Im $A_0/$ Re $A_0= -1.61(28)\times 10^{-4}$。我们对Im\，$A_2$的结果表明，电弱企鹅效应对$ε^\prime/ε$的贡献是Re $(ε^\prime/ε)_{\mathrm{EWP}} = -(6.25 \pm 0.44_{\textrm{stat}} \pm 1.19_{\textrm{syst}}) \times 10^{-4}$.
英文摘要：
We describe the computation of the amplitude A_2 for a kaon to decay into two pions with isospin I=2. The results presented in the letter Phys.Rev.Lett. 108 (2012) 141601 from an analysis of 63 gluon configurations are updated to 146 configurations giving Re$A_2=1.381(46)_{\textrm{stat}}(258)_{\textrm{syst}} 10^{-8}$ GeV and Im$A_2=-6.54(46)_{\textrm{stat}}(120)_{\textrm{syst}}10^{-13}$ GeV. Re$A_2$ is in good agreement with the experimental result, whereas the value of Im$A_2$ was hitherto unknown. We are also working towards a direct computation of the $K\to(ππ)_{I=0}$ amplitude $A_0$ but, within the standard model, our result for Im$A_2$ can be combined with the experimental results for Re$A_0$, Re$A_2$ and $ε^\prime/ε$ to give Im$A_0/$Re$A_0= -1.61(28)\times 10^{-4}$ . Our result for Im\,$A_2$ implies that the electroweak penguin (EWP) contribution to $ε^\prime/ε$ is Re$(ε^\prime/ε)_{\mathrm{EWP}} = -(6.25 \pm 0.44_{\textrm{stat}} \pm 1.19_{\textrm{syst}}) \times 10^{-4}$.
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