Mesonlike baryons and the spin-orbit puzzle

Abstract

I describe a special class of meson-like Λ Q excited states and present evidence supporting the similarity of their spin-independent spectra to those of mesons. I then examine spin-dependent forces in these baryons, showing that predicted effects of spin-orbit forces are small for them for the same reason they are small for the analogous mesons: a fortuitous cancellation between large spin-orbit forces due to one-gluon-exchange and equally large inverted spin-orbit forces due to Thomas precession in the confining potential. In addition to eliminating the baryon spin-orbit puzzle in these states, this solution provides a new perspective on spin-orbit forces in all baryons.

Quark-model study of few-baryon systems

“…This favors a linear form for confinement as also suggested by meson spectroscopy and lattice calculations [160]. We should finally say that the level ordering problem has been cured by means of appropriate phenomenological interactions as has been the case of anharmonic terms [161], scalar three-body forces [162] or pseudoscalar interactions [45,163], but without any connection to a consistent simultaneous description of the baryon-baryon interaction except for reference [163]. [164], applicable only for the ground state of the system, assumes that the ground state three-particle wave function depends on a single variable R = 1 2 (x 1 + x 2 + ηx 3 ), where x i = | r j − r k | with r j,k the particle coordinates and ǫ ijk = 1.…”

Kaon-nucleon interaction in the extended chiral SU(3) quark model

“…In Refs. [17,18], Liu et al produced a valence lattice QCD result which supports the Goldstone boson exchange picture, but Isgur pointed out that this is unjustified [15,16]. On the other hand, in the study of NN interactions on the quark level, the short-range feature can be explained by OGE interaction and quark exchange effect, while in the traditional one-boson exchange (OBE) model on the baryon level it comes from vector-meson (ρ, K * , ω, and φ) exchange.…”

“…They pointed out the spin-flavor interaction is important in explaining the energy of the Roper resonance and got a comparatively good fit to the baryon spectrum. However Isgur gave a critique of the boson exchange model and insisted that the OGE governs the baryon structure [15,16]. In Refs.…”

“…It is a consensus that constituent quark is the dominat effective degree of freedom for low-energy hadron physics, but about what other proper effective degrees of freedom may be there still has been a debate [13,14,15,16,17,18]. Glozman and Riska proposed that the Goldstone boson is the only other proper effective degree of freedom.…”

Mass spectra of doubly heavy baryons in the relativistic quark model

“…The light quark is orbiting around this heavy source at a distance much larger (∼ 1/m q ) than the source size (∼ 2/m Q ). Thus the doubly heavy baryons look effectively like a two-body bound system and strongly resemble the heavy-light B and D mesons [2,13]. Then the HQET expansion in the inverse heavy quark mass can be used.…”