Structure functions and the Gottfried sum from NMC data

The QCD analysis of the Fp2 and Fd2 structure functions obtained by New Muon Collaboration is presented. It leads to precise determination of the gluon distribution down to x=0.008. The re‐evaluation of the Gottfried sum, i.e., the integral ∫(Fp2−Fn2)dx/x,based on better knowledge of the Fd2 at low x, gives at Q2=4 GeV2 value 0.235±0.026(total), significantly smaller than 1/3. This result can be interpreted as flavor symmetry violation in the nucleon sea. Similar conclusion was reached from the analysis of Drell‐Yan asymmetry measured by NA51 experiment at CERN.