Model calculation of nucleon structure functions

Deep inelastic polarized and unpolarized structure functions for a free nucleon are obtained in a modified center-of-mass bag model, which includes the symmetry-breaking effects from spin-dependent interactions. The quark distribution functions, calculated at Q02 congruent(0.9 GeV/c)2, are evolved to a higher Q2 region and compared with the data and other models. The model gives a reasonable description for the valence part of the structure functions at x>0.3. For the small-x region, the contributions from the sea are necessary. The spin-dependent effects are important in describing the existing data