New results on nucleon spin structure from Jefferson Lab

In this talk, we will present the Jefferson Lab (JLab) experimental program on nucleon spin structure. Results from new experiments in JLab's Hall A, B and C, with improved statistical and systematical uncertainties, are becoming available. They complement the results of a first round of experiments that ran in JLab Hall A and B in 1998 by extending the $Q^2$ and Bjorken-$x$ coverages both toward lower and higher limits. The new inclusive results allow us to study the behavior of quark distribution functions at large $x$, to study the transition from the hadronic to quark-gluon descriptions of the nucleon, to shed light on quark-hadron duality, to measure higher twist effects and to check the validity of Chiral Perturbation calculations. They also provide convenient benchmark measurements for lattice QCD calculations. After placing the experiments in their physics context, we will describe their experimental setup and present their results. We will conclude on future measurements with the 12 GeV upgrade of JLab.