paper

Reduced hadronic uncertainty in the determination of

arXiv:1807.10197 · doi:10.1103/PhysRevLett.121.241804

Abstract

We analyze the universal radiative correction to neutron and superallowed nuclear decay by expressing the hadronic -box contribution in terms of a dispersion relation, which we identify as an integral over the first Nachtmann moment of the interference structure function . By connecting the needed input to existing data on neutrino and antineutrino scattering, we obtain an updated value of , wherein the hadronic uncertainty is reduced. Assuming other Standard Model theoretical calculations and experimental measurements remain unchanged, we obtain an updated value of , raising tension with the first row CKM unitarity constraint. We comment on ways current and future experiments can provide input to our dispersive analysis.

5 pages, 5 figures, references updated; version submitted to PRL

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