All you need is N: Baryon spectroscopy in two large N limits

Journal Article · Sat Aug 01 04:00:00 EDT 2009 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.80.036002· OSTI ID:21322401

Cherman, Aleksey; Cohen, Thomas D; Lebed, Richard F ^[1]

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1. Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)

The generalization of QCD to many colors is not unique; each distinct choice corresponds to a distinct 1/N{sub c} expansion. The familiar 't Hooft N{sub c}{yields}{infinity} limit places quarks in the fundamental representation of SU(N{sub c}), while an alternative approach places quarks in its two-index antisymmetric representation. At N{sub c}=3 these two 1/N{sub c} expansions coincide. We compare their predictions for certain observables in baryon spectroscopy, particularly mass combinations organized according to SU(3) flavor breaking. Each large N{sub c} limit generates an emergent spin-flavor symmetry that leads to the vanishing of particular linear combinations of baryon masses at specific orders in the expansions. Experimental evidence shows that these relations hold at the expected orders regardless of which large N{sub c} limit one uses, suggesting the validity of either limit in the study of baryons. We also consider a hybrid large N{sub c} limit in which one flavor is taken to transform in the two-index antisymmetric representation and the rest of the flavors are in the fundamental representation. While this hybrid large N{sub c} limit is theoretically attractive, we show that for a wide class of observables it faces some phenomenological difficulties.

• OSTI ID: 21322401
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 3 Vol. 80; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BARYON SPECTROSCOPY
BARYONS
COMPARATIVE EVALUATIONS
EXPANSION
FLAVOR MODEL
FORECASTING
MASS
QUANTUM CHROMODYNAMICS
QUARKS
SPIN
SU GROUPS
SU-3 GROUPS
SYMMETRY
SYMMETRY BREAKING