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

Abstract

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 $x \sim 0.01$ while it becomes abundant below it.