Speaker
Summary
Neutral Kaon Mixing plays an important role in indirect CP-violation. Together with the epsilon_K experimental observable from kaon decays, it gives a constraint on the unitarity triangle. After an OPE, the box diagrams involved reduce to a matrix element of a deltaS=2 four quark operator, which can be computed in Lattice QCD at high precision, expressed as the so-called 'Kaon bag parameter'. With the recent progresses made in Lattice QCD, all its errors have fallen to the subpercent level except the systematics from renormalisation. In order to reduce this error we have to renormalise to higher and higher scales, which in turn requires having finer lattices, as well as including additional quark flavours in our simulation. We will present the RBC-UKQCD strategy to do so using our newest Nf=2+1+1 ensembles, and the resulting preliminary result for BK and the epsilon_K band.
