Soft pions at high energy as an origin of flavor asymmetry of the light sea quarks in the nucleon

By using the soft pion theorem in the inclusive reactions, soft pions’ contribution to the structure function $F_2$ in the nucleon is estimated. It is shown that this contribution produces such a large flavor asymmetry in the light sea quark distributions that it gives about $30\sim 50$ of the NMC deficit in the Gottfried sum.