Abstract
A global study of the negative parity non-strange baryon observables is performed in the framework of the 1/N{sub c} expansion. Masses, partial decay widths and photo-couplings are simultaneously analyzed. A main objective is to determine the composition of the spin 1/2 and 3/2 nucleon states, which come in pairs and involve two mixing angles which can be determined and tested for consistency by the mentioned observables. The issue of the assignment of those nucleon states to the broken SU(4) X O(3) mixed-symmetry multiplet is studied in detail, with the conclusion that the assignment made in the old studies based on the non-relativistic quark model is the preferred one. In addition, the analysis involves an update of the input data with respect to previous works.
Highlights
The excited baryon states that correspond in the constituent quark model to the first radial and orbital excitations fit well into respectively a positive parity symmetric and a negative parity mixed-symmetric irreducible representation of the spin-flavor group SU (2Nf ), where Nf is the number of light flavors
The determination of the spin-flavor structure of the negative parity baryons is of fundamental importance in the study of excited baryons, as it serves to unravel the QCD dynamics responsible for their properties
Of particular importance is the structure of the J = 1/2 and 3/2 nucleons, which coming in pairs can mix
Summary
The excited baryon states that correspond in the constituent quark model to the first radial and orbital excitations fit well into respectively a positive parity symmetric and a negative parity mixed-symmetric irreducible representation of the spin-flavor group SU (2Nf ), where Nf is the number of light flavors. The negative parity non-strange excited baryons states are empirically the best known ones [1], and are organized in the [20 , = 1] representation of SU (4) × O(3) [2]. Their masses, partial decay widths and photo-couplings are known to a degree where detailed analyses as the one presented here can be carried out and lead to some clear conclusions. In the case of the negative parity baryons, the analysis of the masses suffers from the four-fold ambiguity mentioned above in the assignment of the spin 1/2 and 3/2 nucleon physical states to the theoretical ones. In Ref. [21] they are defined in their Eqs. (18) and (19), which only correspond to the definition Eq (10) when states are assigned according to Set 1 in Eq (11)
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