Gottfried sum rule in QCD NS analysis of DIS fixed target data

Deep inelastic scattering data on $F_2$ structure function obtained in the fixed-target experiments were analysed in the valence quark approximation with a next-to-next-to-leading-order accuracy. Parton distribution functions are parametrized by using information from the Gottfried sum rule. The strong coupling constant is found to be $\alpha_s(M_Z^2) = 0.1180 \pm 0.0020~\mbox(total\,exp.error)$, which coincides very well with the average world value $\alpha_s^{\rm PDG}(M_Z^2) = 0.1181 \pm 0.0013$ updated recently in a PDG report. The result for the second moment of the difference in $u$ and $d$ quark distributions $<\!\!x\!\!>_{u-d}=0.187 \pm 0.021$ is seen to be well compatible with the latest LATTICE result $<\!\!x\!\!>_{u-d}^{\rm LATTICE}=0.208 \pm 0.024$