Calculation of the d/u ratio at large x in the residual mean field model*

We developed a new model to describe the non-singlet patron distribution functions (PDFs) for valence quarks inside the nucleon. In the model three relativistic, massless valence quarks reside in the strong residual field of the nucleon. The calculations are performed using the light front diagrammatic framework. We calculated the down and up valence PDFs covering a range of 0.1 < x < 1. The parameters of the model were fitted to match the PDF peak height and position at x ≈ 0.2. With these parameters we get d_V(x)/u_V (x). The result of d_V(x)/u_V (x)| x→1 ≈ 0.21 is in good agreement with recent data and analyses.  We discuss calculations of other observables.