Reduced Hadronic Uncertainty in the Determination of V_(ud)
We analyze the universal radiative correction Δ^V_R to neutron and superallowed nuclear β decay by expressing the hadronic γW-box contribution in terms of a dispersion relation, which we identify as an integral over the first Nachtmann moment of the γW interference structure function F^((0))_3. By connecting the needed input to existing data on neutrino and antineutrino scattering, we obtain an updated value of Δ^V_R = 0.02467(22), wherein the hadronic uncertainty is reduced. Assuming other standard model theoretical calculations and experimental measurements remain unchanged, we obtain an updated value of |V_(ud)| = 0.97370(14), raising tension with the first row Cabibbo-Kobayashi-Maskawa unitarity constraint. We comment on ways current and future experiments can provide input to our dispersive analysis.
Additional Information© 2018 Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3. Received 16 August 2018; published 14 December 2018. We acknowledge helpful discussions with Bill Marciano, John Hardy, Vincenzo Cirigliano, Peter Blunden, Emmanuel Paschos, Cheng-Pang Liu, Chung-Wen Kao, Hubert Spiesberger, and Jens Erler. Significant progress was made during the scientific program "Bridging the Standard Model to New Physics with the Parity Violation Program at MESA" hosted by MITP Mainz. M. G.'s work was supported by the Deutsche Forschungsgemeinschaft under the personal Grant No. GO 2604/2-1. C. Y. S.'s work is supported in part by the National Natural Science Foundation of China (NSFC) under Grants No. 11575110, No. 11655002, and No. 11735010, Natural Science Foundation of Shanghai under Grants No. 15DZ2272100 and No. 15ZR1423100, by Shanghai Key Laboratory for Particle Physics and Cosmology, and by Key Laboratory for Particle Physics, Astrophysics and Cosmology, Ministry of Education, and also appreciates the support through the Recruitment Program of Foreign Young Talents from the State Administration of Foreign Expert Affairs, China. H. H. P. and M. J. R. M. were supported in part by US Department of Energy Contract No. DE-SC0011095.
Published - PhysRevLett.121.241804.pdf
Submitted - 1807.10197.pdf