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Kaon Theory News

During the last fifteen years B_{s,d} decays, B_{s,d}^0-\bar B^0_{s,d} mixings, CP-violating asymmetries S_{ψK_S} and S_{ψϕ} provided the dominant information about the pattern of flavour violation within the SM and its extensions. We emphasize that in the coming years K meson physics will certainly strike back through the measurements of the branching ratios of theoretically very clean decays K^+->pi^+ν\barνand K_L->π^0ν\barνand improved calculations of the ratio epsilon'/epsilon=\epe. We summarize the status of K^+->pi^+ν\barνand K_L->π^0ν\barνwithin the SM and simplified NP models and update the picture of flavour violation in the Littlest Higgs model with T-parity taking all available constraints into account. But the highlight of this talk are new results on \epe from lattice QCD and large N approach that give a strong indication for a new anomaly in flavour physics, this time coming from K mesons. Indeed, \epe within the SM is found to be significantly below the data of NA48 and KTeV collaborations. Combining lattice results on the non-perturbative parameters B6 and B8 with the assumption that the SM dynamics dominates the Delta I=1/2 rule a 3 sigma anomaly in \epe emerge