Radiatively Generated Isospin Violations in the Nucleon

Abstract

Isospin violating valence and sea distributions are evaluated due to QED leading $\mathcal{O}(\alpha )$ corrections to the standard QCD evolution equations. Unique perturbative predictions are obtained within the radiative parton model, and confirm earlier results. Nonperturbative contributions have been estimated and depend on a single free parameter chosen to be the current quark mass.The relevance of our predictions for extracting ${\sin }^2{\theta }_W$ from DIS $\nu (\bar{\nu })N$ data (`NuTeV anomaly') is discussed as well.

9 pages, 3 figures