Charge asymmetry due to the soft pion at high energy and its effect on   the sea quark
  Using the soft pion theorem in the inclusive reactions, we estimate the soft pion contribution to the structure functions $F_2$ and $g_1$ in the nucleon, and show that it is an indispensable part in these structure functions in the small $x$ region. This contribution is asymmetric for the soft $\pi^+$ and $\pi^-$ due to pole terms in the soft pion limit, hence it is a remnant of the spontaneous chiral symmetry breakings. Then we show that the modified strange sea quark where the soft pion contribution is added to the distribution determined by the ansatz (strange-sea)=(up-sea + down-sea)/4 satisfies the mean charge sum rule for the sea quarks. 
Susumu Koretune