PROTON SPIN STRUCTURE IN THE REST FRAME

It is shown that the quark-parton model in the standard infinite momen tum approach overestimates the proton spin structure function g(1)(x) in comparison with the approach taking consistently into account the i nternal motion of quarks described by a spherical phase space in the p roton rest frame. Particularly, it is shown the first moment of the sp in structure function in the latter approach, assuming only the valenc e quarks contribution to the proton spin. does not contradict the expe rimental data.