Flavor Decomposition of Nucleon Spin Structure: A Proposed Experiment at Jefferson Lab Hall C

We propose to measure the semi-inclusive double-spin asymmetries in deep-inelastic (,eh)X and (,eh)X reactions (h = +, -, K+ and K-) on longitudinally polarized NH3 and LiD targets. The high statistic data will allow a leading order five-flavor decomposition (Delta u, Delta d, Delta u, Delta d, Delta s ) of the nucleon spin structure in the region of x = 0.12 {approx} 0.43 at a Q2 of 1.21 {approx} 3.22 GeV2. The combined spin dependent pi+ + pi- yield ratios will be measured, since the acceptance and the hadron efficiencies of the detectors can be accurately determined. Independent of fragmentation functions and parton distributions, the z-dependence (z = 0.38 {approx} 0.71) of the combined ratios provides a build-in test of factorization at the moderate Q2. We estimate statistical uncertainties associated with such measurements.