Kaon to two pion decays in lattice QCD

Research Team: Elaine Goode, Dirk Broemmel
Investigators: Jonathan Flynn

One of many diagrams we calculate.

Violation of charge-parity (CP) symmetry is observed in our universe: we observe a matter dominated universe rather than detecting equal quantities of matter and antimatter. However, three of the fundamental forces of nature - gravity, electromagnetism and the nuclear strong force are found to respect CP symmetry. Of the remaining weakly interacting processes, only a few of these are found to violate CP symmetry. Furthermore, the standard model of particle physics predicts only a small amount of CP violation, not nearly enough to describe the matter-anitmatter asymmetry we see.

By studying one of the rare CP violating weak decays, in particular the decay of a K-meson (kaon) into pions we can further our understanding of CP violation in the standard model, allowing us to see where new physics can enter the theory. Calculation of the kaon decay width is a non-perturbative problem, so we make use of lattice QCD.

CP violation in kaon decays was first observed over 50 years ago, but only recently have the computer resources that are necessary to tackle the subject from a theoretical point of view been available. This project is a state of the art calculation that will provide a precise standard model prediction that we can compare with the experimental results.

The calculations are performed within the UKQCD and RBC collaborations.

Computational Modelling Group

Kaon to two pion decays in lattice QCD

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