NUCLEON SEA PARTON DENSITIES - DIFFERENCES FOR NEUTRINOS AND MUONS

The nucleon sea parton distributions probed by muons and neutrinos are different since excitation of ssBAR, ccBAR pairs by muons and csBAR, scBAR pairs by neutrinos have different mass thresholds. Natural starting points for the structure functions are c(v)(x, Q2) almost-equal-to s(v)(x, Q2), in v (vBAR) interactions and c-mu(x, Q2) << s-mu(x, Q2) in mu-interactions. Up to approximately 20% corrections to the conventional predictions for the neutrino structure functions at small x are predicted. The effects we discuss are in leading twist and persist numerically up to large values of Q2.