English

Current status of $\varepsilon_K$ with lattice QCD inputs

High Energy Physics - Lattice 2015-04-14 v3 High Energy Physics - Phenomenology

Abstract

We present the Standard Model evaluation of the indirect CP violation parameter εK\varepsilon_K using inputs determined from lattice QCD together with experiment: Vus|V_{us}|, Vcb|V_{cb}|, ξ0\xi_0, and B^K\hat{B}_K. We use the Wolfenstein parametrization (Vcb|V_{cb}|, λ\lambda, ρˉ\bar{\rho}, ηˉ\bar{\eta}) for the CKM matrix elements. For the central value, we take the angle-only fit of the UTfit collaboration, and use Vus|V_{us}| from the K3K_{\ell 3} and Kμ2K_{\mu 2} decays as an independent input to fix λ\lambda. For the error estimate, we use results of the global unitarity triangle fits from the CKMfitter and UTfit collaborations. We find that the Standard Model (SM) prediction of εK\varepsilon_K with exclusive VcbV_{cb} (lattice QCD results) is lower than the experimental value by 3.6(2)σ3.6(2)\sigma. However, with inclusive VcbV_{cb} (results of the heavy quark expansion), the tension between the SM prediction of εK\varepsilon_K and its experimental value disappears.

Keywords

Cite

@article{arxiv.1503.06613,
  title  = {Current status of $\varepsilon_K$ with lattice QCD inputs},
  author = {Jon A. Bailey and Yong-Chull Jang and Weonjong Lee and Sungwoo Park},
  journal= {arXiv preprint arXiv:1503.06613},
  year   = {2015}
}

Comments

5 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:1503.05388

R2 v1 2026-06-22T08:59:26.532Z