Power corrections to the CP-violation parameter εK

We present the calculation of the short-distance power corrections to the CP-violation parameter εK coming from dimension-8 operators in the ∆S = 2 effective Hamiltonian. A first estimate of this contribution, obtained for large-Nc and in the chiral limit, was provided in ref. [1]. Here we evaluate and include the $$ \mathcal{O}\left({m}_K^2/{m}_c^2\right) $$ O m K 2 / m c 2 and $$ \mathcal{O}\left({\Lambda}_{\mathrm{QCD}}^2/{m}_c^2\right) $$ O Λ QCD 2 / m c 2 contributions that, a priori, could induce $$ \mathcal{O} $$ O (1) corrections to previous estimates, as mK is numerically of order ΛQCD. Our computation shows that there are several dimension-8 operators besides the one considered before. Their effect on εK, however, accidentally cancels out to a large extent, leaving the final correction at the level of 1%.