William Marciano

Brookhaven National Laboratory

CKM Unitarity, Nuclear Beta Decay and The Bjorken Sum Rule


Electroweak radiative corrections to super-allowed nuclear beta decays are discussed. Their connection to the Bjorken Sum Rule in polarized electron scattering is described and used to reduce theoretical uncertainties. As a result, one finds Vud = 0.9739(3) which when combined with Vus results from kaon decays confirms CKM unitarity at the level of quantum loop effects. Implications for "New Physics" and possible future advances are briefly outlined.

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