Mesonlike baryons and the spin-orbit puzzle - art. no. 014025

I describe a special class of mesonlike Lambda(Q) excited states and presen t evidence supporting the similarity of their spin-independent spectra to t hose of mesons. I then examine spin-dependent forces in these baryons, show ing that the baryon spin-orbit puzzle is solved for them for the same reaso n spin-orbit forces are small for the analogous mesons: a fortuitous cancel lation between large spin-orbit forces due to one-gluon exchange and equall y large inverted spin-orbit forces due to Thomas precession in the confinin g potential. This solution provides a new perspective on spin-orbit forces in all baryons by showing that the three-body spin-orbit forces which were believed to be the origin of the baryon spin-orbit problem conspire in thes e states to become an essential part of this cancellation.