Role of Positivity Constraints in Determining Polarized Parton Densities

We have re-analyzed the world data on inclusive polarized DIS, in both NLO and LO QCD, including the very precise JLab Hall A neutron data, and have studied the role of positivity constraints, and demonstrated their importance, in determining the strange and gluon densities. We have shown that higher twist corrections are essential in the analysis of the present data on the structure function g1. A consistent QCD analysis is achieved, and results for the polarized parton densities are given in both the MSbare and JET schemes.