Five-quark components in baryons

Abstract

Evidence has been accumulating for the existence of significant intrinsic non-perturbative five-quark components in various baryons. The inclusion of the five-quark components gives a natural explanation of the excess of $\bar d$ over $\bar u$, significant quark orbital angular momentum in the proton, the problematic mass and decay pattern of the lowest $1/2^-$ baryon nonet, etc.. A breathing mode of $qqq\leftrightarrow qqqq\bar q$ is suggested for the lowest $1/2^-$ baryon octet. Evidence of a predicted member of the new scheme, $\Sigma^*(1/2^-)$ around 1380 MeV, is introduced.