Rare Kaon Decay Experiments

在欧洲核子研究中心（CERN）的NA62实验中，高精度测量超稀有的K+到π +的中微子反中微子（KPNN）将是夸克味物理最敏锐的探测之一。分支比对许多其他反应所不能达到的新物理模型很敏感，这些模型扩展了标准模型，解决了标准模型的许多问题。对于KPNN分支分数的SM预测被广泛认为在5%的水平上是理论上鲁棒的。只有极少数可获得的环主导夸克过程能够以这种确定性进行预测。将SM中的KPNN分支分数抑制到10-10的水平，使得SM之外的物理对分支分数的贡献显著增加，比SM预测的分支分数提高了5倍。SM对KPNN的贡献的确定性可以预测，这将允许在夸克风味物理中具有独特灵敏度的新物理的重大发现潜力，并且它允许在大型强子对撞机的范围内探测与夸克耦合的大多数新物理模型。此外，KPNN的高精度测量对许多新物理模型很敏感，这些模型的质量尺度远远超出了LHC的直接范围。NA62期望在SM水平上对KPNN具有观测100个事件的灵敏度，覆盖了新物理模型贡献的大部分参数空间。它还将研究许多其他罕见或禁止的反应，以寻找暗物质、重惰性中微子、中性介子衰变和辐射过程。

High precision measurement of the ultra-rare kaon decay K+ to pi+ neutrino anti-neutrino (KPNN) at the CERN NA62 experiment will be one of the most incisive probes of quark flavor physics. The branching ratio is sensitive to many new physics models not accessible by other reactions which extend the Standard Model (SM) to solve its considerable problems. The SM prediction for the KPNN branching fraction is broadly recognized to be theoretically robust at the 5% level. Only a precious few accessible loop-dominated quark processes can be predicted with this level of certainty. The suppression of the KPNN branching fraction in the SM to the level 10-10 allows physics beyond the SM to contribute dramatically to the branching fraction with enhancements of up to factors of five above SM predictions. The certainty with which the SM contribution to KPNN can be predicted will permit a significant discovery potential for new physics with sensitivity unique in quark flavor physics and it allows probing of most models of new physics that couple to quarks within the reach of the LHC. Furthermore, a high precision measurement of KPNN is sensitive to many models of new physics with mass scales well beyond the direct reach of the LHC. NA62 expects to have sensitivity for observing 100 events at the SM level for KPNN covering most of the parameter space for new physics models to contribute. It will also study many other rare or forbidden reactions to search for dark matter, heavy sterile neutrinos, neutral pion decays, and radiative processes.