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, ${\Sigma }^{\ast }(1/2^{-})$ around 1380 MeV, is introduced.

Comments: invited plenary talk at the 10th International Conference on Hypernuclear and Strange Particle Physics (HypX09) September 14th - 18th, 2009, Tokai, Ibaraki, Japan