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arXiv · 1911.01359

Isospin-Violating Contributions to $\epsilon'/\epsilon$

V. Cirigliano·H. Gisbert·A. Pich·A. Rodríguez-Sánchez
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Abstract

The known isospin-breaking contributions to the $K\rightarrow \pi\pi$ amplitudes are reanalyzed, taking into account our current understanding of the quark masses and the relevant non-perturbative inputs. We present a complete numerical reappraisal of the direct CP-violating ratio $\epsilon'/\epsilon$, where these corrections play a quite significant role. We obtain the Standard Model prediction $\text{Re}\left(\epsilon'/\epsilon\right)\, =\,\left(14\,\pm\,5\right)\cdot 10^{-4}$, which is in very good agreement with the measured ratio. The uncertainty, which has been estimated conservatively, is dominated by our current ignorance about $1/N_C$-suppressed contributions to some relevant chiral-perturbation-theory low-energy constants.

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V. Cirigliano, H. Gisbert, A. Pich, A. Rodríguez-Sánchez. 2019-11-04. Isospin-Violating Contributions to $\epsilon'/\epsilon$. https://doi.org/10.1007/jhep02(2020)032

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