The non-perturbative constraint on sea quarks: the strange sea quarks in the nucleon and the soft pion contribution at high energy

The mean charge sum rule for the light sea quarks in the nucleon which holds under the same theoretical footing as the modified Gottfried sum rule shows that a usual parameterization of the strange sea quark distribution underestimate its contribution in the small x region. We give a discussion of the soft pion contribution at high energy as a possible explanation of the saturation of the sum rule and show that it naturally explains why the strange sea quark is suppressed in the region above x ∼ 0.01 while it becomes abundant below it.