Vector Anomaly Revisited in the Anomalous Magnetic Moment of W ± Bosons

In the calculation of the anomalous magnetic moment of W ± bosons, we discuss vector anomalies occuring in the fermion loop that spoil the predictive power of the theory. While the previous analyses were limited to using essentially the manifestly covariant dimensional regularization method, we extend the analysis using both the manifestly covariant formulation and the light-front hamiltonian formulation with several different regularization methods. In the light-front dynamics (LFD), we find that the zero-mode contribution to the helicity zero-to-zero amplitude for the W ± gauge bosons is crucial for the correct calculations. Further, we confirm that the anomaly-free condition found in the analysis of the axial anomaly can also get rid of the vector anomaly in LFD as well as in the manifestly covariant calculations. Our findings in this work may provide a bottom-up fitness test not only to the LFD calculations but also to the theory itself, whether it is any extension of the Standard Model or an effective field theoretic model for composite systems.