Physics Department, University of Connecticut, Storrs, Connecticut 06269-3046, USA.
Phys Rev Lett. 2012 Apr 6;108(14):141601. doi: 10.1103/PhysRevLett.108.141601. Epub 2012 Apr 4.
We report on the first realistic ab initio calculation of a hadronic weak decay, that of the amplitude A(2) for a kaon to decay into two π mesons with isospin 2. We find ReA(2)=(1.436±0.063(stat)±0.258(syst))10(-8) GeV in good agreement with the experimental result and for the hitherto unknown imaginary part we find ImA(2)=-(6.83±0.51(stat)±1.30(syst))10(-13) GeV. Moreover combining our result for ImA(2) with experimental values of ReA(2), ReA(0), and ε'/ε, we obtain the following value for the unknown ratio ImA(0)/ReA(0) within the standard model: ImA(0)/ReA(0)=-1.63(19)(stat)(20(syst)×10(-4). One consequence of these results is that the contribution from ImA(2) to the direct CP violation parameter ε' (the so-called Electroweak Penguin contribution) is Re(ε'/ε)(EWP)=-(6.52±0.49(stat)±1.24(syst))×10(-4). We explain why this calculation of A(2) represents a major milestone for lattice QCD and discuss the exciting prospects for a full quantitative understanding of CP violation in kaon decays.
我们报告了第一个真实的从头算强子弱衰变振幅，即 K 介子衰变为两个同位旋为 2 的π介子的 A(2)振幅。我们发现 ReA(2)=(1.436±0.063(stat)±0.258(syst))10(-8) GeV，与实验结果非常吻合，对于迄今未知的虚部，我们发现 ImA(2)=-(6.83±0.51(stat)±1.30(syst))10(-13) GeV。此外，我们将 ImA(2)的结果与 ReA(2)、ReA(0)和 ε'/ε 的实验值相结合，在标准模型内得到了未知比值 ImA(0)/ReA(0)的以下值：ImA(0)/ReA(0)=-1.63(19)(stat)(20(syst)×10(-4)。这些结果的一个后果是，ImA(2)对直接 CP 破坏参数 ε'（所谓的电弱企鹅贡献）的贡献为 Re(ε'/ε)(EWP)=-(6.52±0.49(stat)±1.24(syst))×10(-4)。我们解释了为什么 A(2)的这种计算代表了格点 QCD 的一个重要里程碑，并讨论了全面理解 K 介子衰变中 CP 破坏的令人兴奋的前景。
