Theory Colloquium

# ε' / ε, K → π  ν  ν̅, and ΔΜ_Κ: Standard Model and BeyondCancelled

## by Andrzej Buras (Munich)

Europe/Zurich
Description

After a short Introduction to the Kaon physics I will summarize in non-technical terms the Dual QCD approach used since 1980s for the evaluation of hadronic matrix elements entering the ratio  ε'/ε. I will recall its successes as far as K^0--\bar{K}^0 mixing  and the ΔI=1/2 rule in K→ππ decays are concerned. I will then show the arguments based on Dual QCD approach and NNLO QCD corrections to electroweak penguin contributions as well as isospin breaking effects why Jean-Marc Gérard and myself claim that there is an anomaly in ε'/ε and why we disagree with Chiral Perturbation analyses which claim that there is no anomaly. Whether we will know by April 22nd the result  for ε'/ε from RBC-UKQCD lattice QCD collaboration is an interesting question. Assuming the presence of this anomaly I will discuss briefly possible new physics responsible for it. Finally the links of this anomaly to rare decays  K → π ν ν̅ and the K_L-K_S mass difference ΔΜ_Κ will be discussed in the context of simple new physics scenarios.