arXiv 0710.30482007-10-16hep-ph

尖点效应与Kl4衰变的理论进展

Theoretical progress on cusp effect and Kl4 decays

J. Gasser

备注：: Plenary talk given at the International Conference KAON'07, Laboratori Nazionali di Frascati, Italy, May 21-25, 2007. To appear in the proceedings. 10 pages, 3 figures
发表信息：: PoSKAON:033,2008

摘要：

K \to 3π中的尖点效应和K_e 4衰变的数据使人们能够提取阈值附近弹性ππ散射振幅的实验信息，并将分析结果与QCD框架下的预言相对照。在我的演讲中，我指出，这些预测涉及一个同位旋对称的世界，而实验是在现实世界中进行的，在现实世界中，由电磁相互作用和上下夸克的质量差产生的同位旋破缺效应总是存在的。我讨论了解释这些问题所需的修正，以便与预测进行有意义的比较。特别指出，在K_e4衰变中存在一种迄今被忽视的奇特的同位旋破缺效应。一旦考虑到这一点，之前NA 48/2的K_e4衰变数据和ππ散射长度预测之间的差异就消失了。

英文摘要：

The cusp effect in K \to 3πand data on K_e4 decays allow one to extract experimental information on the elastic ππscattering amplitude near threshold, and to confront the outcome of the analyses with predictions made in the framework of QCD. In my talk I pointed out that these predictions concern an isospin symmetric world, while experiments are carried out in the real world, where isospin breaking effects -- generated by electromagnetic interactions and by the mass difference of the up and down quarks -- are always present. I discussed the corrections required to account for these, so that a meaningful comparison with the predictions becomes possible. In particular, I pointed out that there is a spectacular isospin breaking effect in K_e4 decays, overlooked so far. Once it is taken into account, the previous discrepancy between NA48/2 data on K_e4 decays and the prediction of ππscattering lengths disappears.

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英文摘要：

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