Structure of the nucleon's low-lying excitations

Abstract

A continuum approach to the three valence-quark bound-state problem in quantum field theory is used to perform a comparative study of the four lightest $(I=1/2,J^P=1/2^{\pm })$ baryon isospin-doublets in order to elucidate their structural similarities and differences. Such analyses predict the presence of nonpointlike, electromagnetically-active quark-quark (diquark) correlations within all baryons; and in these doublets, isoscalar-scalar, isovector-pseudovector, isoscalar-pseudoscalar, and vector diquarks can all play a role. In the two lightest $(1/2,1/2^{+})$ doublets, however, scalar and pseudovector diquarks are overwhelmingly dominant. The associated rest-frame wave functions are largely $S$-wave in nature; and the first excited state in this $1/2^{+}$ channel has the appearance of a radial excitation of the ground state. The two lightest $(1/2,1/2^{-})$ doublets fit a different picture: accurate estimates of their masses are obtained by retaining only pseudovector diquarks; in their rest frames, the amplitudes describing their dressed-quark cores contain roughly equal fractions of even- and odd-parity diquarks; and the associated wave functions are predominantly $P$-wave in nature, but possess measurable $S$-wave components. Moreover, the first excited state in each negative-parity channel has little of the appearance of a radial excitation. In quantum field theory, all differences between positive- and negative-parity channels must owe to chiral symmetry breaking, which is overwhelmingly dynamical in the light-quark sector. Consequently, experiments that can validate the contrasts drawn herein between the structure of the four lightest $(1/2,1/2^{\pm })$ doublets will prove valuable in testing links between emergent mass generation and observable phenomena and, plausibly, thereby revealing dynamical features of confinement.

13 pages, 6 figures, 1 table

References in corpus (18)

• Baryons as relativistic three-quark bound states
• Sketching the Bethe-Salpeter kernel
• Bridging a gap between continuum-QCD and ab initio predictions of hadron observables
• Dressed-quark anomalous magnetic moments
• Dynamical Coupled-Channel Model of $\pi N$ Scattering in the W $\le$ 2 GeV Nucleon Resonance Region
• Meson screening masses from lattice QCD with two light and the strange quark
• Masses of ground and excited-state hadrons
• Perspective on rainbow-ladder truncation
• Natural constraints on the gluon-quark vertex
• On light baryons and their excitations
• Parton distribution amplitudes of light vector mesons
• Exciting flavored bound states
• Parity partners in the baryon resonance spectrum
• Dissecting nucleon transition electromagnetic form factors
• Measurements of $ep\to e^{\prime }{\pi }^{+}{\pi }^{-}{p}^{\prime }$ Cross Sections with CLAS at $1.40<W<2.0$ GeV and $2.0<Q^2<5.0$ GeV${}^2$
• Leading-twist distribution amplitudes of scalar- and vector-mesons
• Revisiting the Vector and Axial-vector Vacuum Susceptibilities
• Roper resonance -- solution to the fifty year puzzle

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