D'Ambrosio Giancarlo, Kitahara Teppei
INFN-Sezione di Napoli, Via Cintia, 80126 Napoli, Italy.
Institute for Theoretical Particle Physics (TTP), Karlsruhe Institute of Technology, Engesserstraße 7, D-76128 Karlsruhe, Germany.
Phys Rev Lett. 2017 Nov 17;119(20):201802. doi: 10.1103/PhysRevLett.119.201802. Epub 2017 Nov 14.
A rare decay K_{L}→μ^{+}μ^{-} has been measured precisely, while a rare decay K_{S}→μ^{+}μ^{-} will be observed by an upgrade of the LHCb experiment. Although both processes are almost CP-conserving decays, we point out that an interference contribution between K_{L} and K_{S} in the kaon beam emerges from a genuine direct CP violation. It is found that the interference contribution can change K_{S}→μ^{+}μ^{-} standard-model predictions at O(60%). We also stress that an unknown sign of A(K_{L}→γγ) can be determined by a measurement of the interference, which can much reduce a theoretical uncertainty of B(K_{L}→μ^{+}μ^{-}). We also investigate the interference in a new physics model, where the ε_{K}^{'}/ε_{K} tension is explained by an additional Z-penguin contribution.
罕见衰变(K_{L}→μ^{+}μ^{-})已被精确测量，而罕见衰变(K_{S}→μ^{+}μ^{-})将通过大型强子对撞机底夸克实验（LHCb实验）的升级进行观测。尽管这两个过程几乎都是CP守恒衰变，但我们指出，在K介子束中(K_{L})和(K_{S})之间的干涉贡献源自真正的直接CP破坏。研究发现，该干涉贡献可在O(60%)的量级上改变(K_{S}→μ^{+}μ^{-})的标准模型预测。我们还强调，通过对干涉的测量可以确定(A(K_{L}→γγ))的未知符号，这可以大大降低(B(K_{L}→μ^{+}μ^{-}))的理论不确定性。我们还在一个新物理模型中研究了这种干涉，在该模型中，(\varepsilon_{K}^{'}/\varepsilon_{K})的张力由额外的Z企鹅贡献来解释。
