Nucleon Viewed as a Borromean Bound-State
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We explain how the emergent phenomenon of dynamical chiral symmetry breaking ensures that Poincaré covariant analyses of the three valence–quark scattering problem in continuum quantum field theory yield a picture of the nucleon as a Borromean bound-state, in which binding arises primarily through the sum of two separate contributions. One involves aspects of the non-Abelian character of Quantum Chromodynamics that are expressed in the strong running coupling and generate tight, dynamical color-antitriplet quark–quark correlations in the scalar–isoscalar and pseudovector-isotriplet channels. This attraction is magnified by quark exchange associated with diquark breakup and reformation, which is required in order to ensure that each valence–quark participates in all diquark correlations to the complete extent allowed by its quantum numbers. Combining these effects, we arrive at a properly antisymmetrised Faddeev wave function for the nucleon and calculate, e.g. the flavor-separated versions of the Dirac and Pauli form factors and the proton’s leading-twist parton distribution amplitude. We conclude that available data and planned experiments are capable of validating the proposed picture.
Work supported by: European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 665919; Spanish MINECO’s Juan de la Cierva-Incorporación programme with Grant Agreement No. IJCI-2016-30028; Spanish Ministerio de Economía, Industria y Competitividad under Contract Nos. FPA2014-55613-P and SEV-2016-0588; the Chinese Government’s Thousand Talents Plan for Young Professionals; and U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
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