Determination of ϵK using lattice QCD inputs

Jon A. Bailey, Yong Chull Jang, Weonjong Lee, Sungwoo Park

Research output: Contribution to journalConference articlepeer-review

3 Citations (Scopus)


We present results for the indirect CP violation parameter ϵK determined directly from the standard model using lattice QCD to fix the inputs BK, ξ0, Vus, and jVcbj. We use the FLAG and SWME results for BK. We use the RBC-UKQCD result for ξ0 determined using the experimental value of ϵ1/ϵ and the lattice result of ImA2. To set the Wolfenstein parameter λ, we use /Vus, which is determined from Kℓ3 and Kmμ2 decays combined with lattice evaluations of the K →πℓν vector form factor and fK. To set the Wolfenstein parameter A, we use the FNAL/MILC results for /Vcb, which are determined from the exclusive decay B→Dℓν and the axial form factor at zero recoil. We also use the inclusive /Vcb obtained using the heavy quark expansion based on QCD sum rules and the OPE. We compare the results with those for exclusive /Vcb. We find that the standard model prediction of ϵK with exclusive /Vcb (lattice QCD results) is lower than the experimental value by 3.4σ. However, we observe no tension in ϵK determined from inclusive /Vcb.

Original languageEnglish
Article number348
JournalProceedings of Science
Publication statusPublished - 2015
Event33rd International Symposium on Lattice Field Theory, LATTICE 2015 - Kobe, Japan
Duration: 2015 Jul 142015 Jul 18

Bibliographical note

Funding Information:
Y.C.J. thanks A. Soni for helpful discussion on the unitarity triangle analysis. We thank J. Brod and A. J. Buras for a helpful discussion on ηcc. The research of W. Lee is supported by the Creative Research Initiatives Program (No. 2015001776) of the NRF grant funded by the Korean government (MEST). J.A.B. is supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2015024974). W. Lee would like to acknowledge the support from the KISTI supercomputing center through the strategic support program for the supercomputing application research (No. KSC-2014-G3-002). Computations were carried out on the DAVID GPU clusters at Seoul National University.

All Science Journal Classification (ASJC) codes

  • General


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