Baryon Effective Theories and Phenomenology in the 1/N_C Expansion

Thesis/Dissertation · Fri Dec 08 00:00:00 EST 2017

DOI:https://doi.org/10.2172/1574221· OSTI ID:1574221

Fernando, Madappuli Arachchige Ishara ^[1]

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1. Hampton Univ., Hampton, VA (United States)

Chiral perturbation theory (ChPT) and the 1/N_C expansion provide systematic frameworks to investigate the strong interaction at low energy. There are two main focuses of this dissertation. First, analyzing the masses of baryons in the framework of the 1/N_C expansion, using the available physical masses and masses calculated in lattice QCD. Second, combining both ChPT and the 1/N_C expansion into a single framework and applying it to the phenomenology of baryons with three light-quark flavors. In the first focus, the baryon states are organized into irreducible representations of SU(6)×O(3), where the [56,ℓ^P = 0⁺] contains the ground state and radially excited baryons, and the [56,2⁺] and [70,1^-] contain orbitally excited states are analyzed. The analyses are carried out to O(1/N_C) and first order in the quark masses. The issue of state identifications is discussed. Numerous parameter independent mass relations and the famous Gell-Mann-Okubo (GMO) and Equal-Spacing (ES) relations are tested. Also, the quark mass dependence of the operator coefficients for baryon mass is discussed. In the second focus, a small scale expansion of the combined approach is defined as the ξ-expansion, in which the power counting of 1/N_C and chiral expansions are linked as O(p) = O(1/N_C) = O(ξ). A calculation of one-loop corrections to the ground state baryon masses, vector and axial-vector currents up to O(x&i;³) is presented. Moreover, the physical and lattice QCD masses are considered in order to understand the quark mass dependence, along with an analysis of the violations to GMO, ES and Gürsey-Radicati (GR) mass relations, and their dependence on N_C.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1574221
• Report Number(s): JLAB-PHY-19-3071; DOE/OR/23177-4826; NSF PHY-0855789; NSF PHY-1307413; NSF PHY-1613951
• Country of Publication: United States
• Language: English