Speaker
Description
We report our recent results for $K\to\pi\pi$ matrix elements and $\varepsilon'$, the measure of direct CP violation, released on arXiv:2306.06781. This is RBC/UKQCD's first result for $\varepsilon'$ with periodic boundary conditions (PBC), while our earlier calculations were performed with G-parity boundary conditions, where the isospin-0 two-pion ground state corresponds to the on-shell kinematics. Using the GEVP method with multiple two-pion operators, we overcome the difficulty that PBC require us to calculate the matrix elements with excited two-pion final states to obtain the on-shell kinematics. We therefore continue measurements with more configurations and on finer lattices to improve the precision. This talk includes the report on the latest status of new calculations.
| Topical area | Quark and Lepton Flavor Physics |
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