Discriminating between chiral models of the nucleon via hard semi-inclusive e⃗N⃗and N⃗N⃗scattering

Measurements of the flavor asymmetry of the polarized antiquark distributions in the nucleon, Δū(x)−Δd(x), would provide a unique opportunity to discriminate between different models of the role of the chiral structure of the nucleon in deep-inelastic scattering. In the pion cloud model of the nucleon’s sea quark distributions the polarized flavor asymmetry is zero, while the large-Nc picture of the nucleon as a chiral soliton predicts large polarized flavor asymmetries. We discuss the prospects for measuring the polarized antiquark flavor asymmetries in two types of semi-inclusive scattering experiments: i) Hadron production in semi-inclusive polarized eN scattering (SMC, HERMES); ii) Drell-Yan lepton pair production in polarized NN scattering at HERA or RHIC energies. In particular, the Drell-Yan spin asymmetries are shown to be remarkably sensitive to Δū(x)−Δd(x).