ANOMALOUS EVOLUTION OF NONSINGLET NUCLEON STRUCTURE FUNCTIONS

We calculate the scale dependence of nonsinglet nucleon structure, fun ctions. Due to anomalous axial symmetry breaking a large flavour asymm etry of the quark-antiquark sea is generated nonperturbatively. This p roduces a strong scale dependence of the nonsinglet structure function in an intermediate range of Q2 . Evolving nonperturbatively a pure va lence distribution from an infrared scale we can thus compute F2p - F2 n as measured by the NMC, and give detailed predictions for its Q2 dep endence at fixed x. We also compare our results with Drell-Yan data.