Chiral symmetry and the charge asymmetry of thess¯distribution in the proton

Recently it has been suggested that a sizeable fraction of the strange and charm quarks in a nucleon–the so-called ‘‘intrinsic strangeness or charm’’–have momentum distributions which extend to large ${\mathit{x}}_{\mathit{b}\mathit{j}}$. This effect is enhanced if these virtual heavy quarks live long enough so that many interactions with the rest of the nucleon can occur. It is shown that the same mechanism responsible for the intrinsic component also leads to a sizeable charge asymmetry of the corresponding spin and momentum distributions.