We report a strong tension in μK at the 4σ level between the experimental value and the theoretical value calculated directly from the standard model using lattice QCD inputs such as B^K, |Vcb|, |Vus|, ξ0, ξ2, ξLD, FK, and mc. The standard model with lattice QCD inputs describes only 70% of the experimental value of μK, and does not explain its remaining 30%. We also find that this tension disappears when we use the inclusive value of |Vcb| (results of the heavy quark expansion based on QCD sum rules) to determine μK. This tension is highly correlated with the present discrepancy between the exclusive and inclusive values of |Vcb|. In order to resolve, in part, the issue with |Vcb|, it would be highly desirable to have a comprehensive reanalysis over the entire set of experimental data on the B→D∗ ν decays using an alternative parametrization of the form factors, such as the Boyd, Grinstein, and Lebed parametrization, and a comparison with results of the Caprini, Lellouch, and Neubert method.
Bibliographical noteFunding Information:
We express our sincere gratitude to Carleton Detar, Aida El-Khadra, and Andreas Kronfeld for helpful discussions. We also express sincere gratitude to Guido Martinelli for providing us with the most updated results of UTfit. The research of W. L. is supported by the Creative Research Initiatives Program (Grant No. 2017013332) of the National Research Foundation of Korea (NRF) grant funded by the Korean government (MEST). W. L. acknowledges the support from the KISTI supercomputing center through the strategic support program for the supercomputing application research (Grant No. KSC-2015-G2-0002). Computations were carried out on the DAVID GPU clusters at Seoul National University. J. A. B. is supported by the Basic Science Research Program of the NRF funded by the Ministry of Education (Grant No. 2014027937).
© 2018 authors. Published by the American Physical Society.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)