${\Lambda }_s(1405)$ and Negative Parity Baryon States

Abstract

After a brief historical background on the $\text{Ls}$, we revisit the 25 year old controversy on whether $\text{Ls}$ is a $qqq$ (L=1) three quark state or a $\text{K}$ quasi virtual bound state. This work is stimulated by the recent suggestion of Isgur that s be treated as a heavy quark in heavy quark effective theory HQET. We re-examine the empirical evidence for minimal mixing amongst singlets and octets in negative parity baryon states, with a possible dynamical origin in the opening of inelastic threshold channels. Finally, we suggest that $\text{Ls}$ belongs to a class of hadrons which are described simultaneously as $qqq$ or $q\bar{q}$ states and as hadronic bound states.

Comments: 11 pages, LATEX format