Accurate Verification of the Conserved-Vector-Current and Standard-Model Predictions

Abstract

An approximate analytic calculation of $O\left(Z{\alpha }^2\right)$ corrections to Fermi decays is presented. When the analysis of Koslowsky et al. is modified to take into account the new results, it is found that each of the eight accurately studied $\mathcal{F}t$ values differs from the average by $\lesssim 1\sigma$, thus significantly improving the comparison of experiments with conserved-vector-current predictions. The new $\mathcal{F}t$ values are lower than before, which also brings experiments into very good agreement with the three-generation standard model, at the level of its quantum corrections.