Flavor asymmetry of the polarized nucleon sea

We discuss the flavor asymmetry of polarized light antiquarks in the nucleon, uδ-δu. W present a determination of this quantity based on two global QCD analyses of experimental data DSSV08 and NNPDFpol1.1, in which sea-quark parton distribution functions are determine respectively either from semi-inclusive deep-inelastic scattering orW-boson production data. Th latter have become available only very recently, and their effect on the polarized flavor asymmetr is presented here for the first time. We find that the flavor asymmetry of polarized antiquarks in th nucleon is definitely positive, and has almost the same absolute size of its unpolarized counterpart We compare this result with various theoretical models of the nucleon structure in order to tes their validity. We show that some of them are clearly disfavored.