Can we measure [formula omitted] in semi-inclusive eN or NN scattering?

Abstract

The flavor asymmetries of the polarized antiquark distributions in the nucleon, Δ u(x) - Δ d(x) and Δ u(x) + Δ d(x) - 2Δ s , cannot be measured in inclusive DIS alone. Large flavor asymmetries have been predicted by model calculations of the polarized parton distributions at a low normalization point in the large- N c limit (chiral quark-soliton model of the nucleon). We discuss the prospects for measuring these flavor asymmetries in two types of semi-inclusive 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 Δ u(x) - Δ d(x) .