Matter-Antimatter Asymmetry in Neutral Kaons
Graduate Research Assistant
University of Cincinnati
The parameter εK is an important measure of the imbalance between matter and antimatter in the neutral kaon system. In particular, εK provides a sensitive probe of new physics and plays a critical role in the global fit of the Cabibbo-Kobayashi-Maskawa matrix. As one of the first discovered sources of CP violation, it has been extensively measured in experiment to per-mil precision. The theoretical calculation of εK, however, has historically been plagued by large perturbative errors arising from charm-quark corrections. These errors were larger than the expected magnitude of higher-order electroweak corrections in perturbation theory, rendering these contributions irrelevant. Recently, it was discovered that a simple re-parameterization of the theory drastically reduces perturbative errors, making these higher-order electroweak calculations worthwhile. We present the two-loop electroweak contributions from the top quark to εK. In the traditional normalization of the weak Hamiltonian, this results in a -1% shift in the top quark contribution.
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