Evidence for charge symmetry violation in parton distributions - art. no. 074021

By comparing structure functions measured in neutrino and charged lepton de ep inelastic scattering, one can test the validity of parton charge symmetr y. New experiments allow us to make such tests, which set rather tight uppe r limits on parton charge symmetry violation (CSV) for intermediate Bjorken x, but which appear to show sizable CSV effects at small x. We show that n either nuclear shadowing nor contributions from strange and antistrange qua rk distributions can account for the experimentally observed difference bet ween the two structure functions. We are therefore forced to consider the p ossibility of a large CSV effect in the nucleon sea quark distributions. We discuss the consequences of this effect for other observables, and we prop ose an experiment which could detect a large CSV component in the nucleon s ea. [S0556-2821(99)03507-9].