corrections to the baryon axial currents in QCD

Abstract

We prove that the 1/N c corrections to the baryon axial current matrix elements are proportional to their lowest order values. This implies that the first correction to axial current coupling constant ratios vanishes, and that the SU (2N f ) spin-flavor symmetry relations are only violated at second order in 1/N c . UCSD/PTH 93-18

Baryon vector current in the chiral and1/Ncexpansions

“…As it is well known from the consistency constraints imposed by the large-N c limit of QCD for baryons [23], it is necessary to include on an equal footing in the effective theory the octet and the decuplet baryons, as demanded by the emergent spin-flavor symmetry (SU(6)) in the large-N c limit which is a consequence of that consistency. The interplay of these multiplets in chiral loops is often necessary to restore the correct N c power counting, by producing exact cancellations of otherwise power counting violating contributions.…”

Model-independent form factor relations at largeNc

“…They are a generalization of Pauli matrices, which appear in the pionnucleon-nucleon vertex in standard χPT [28]. The form of the couplings is determined by the consistency relations of large N c QCD [11,12]. Simply, the interaction is of the same form as standard pion-nucleonnucleon (vector-isovector) where ordinary 2×2 Pauli matrices (τ and σ) are replaced by the properly normalized (2J ′ + 1) × (2J + 1) matrices (τ BB ′ and σ BB ′ ) whose elements are given by the Clebsch-Gordan coefficients (see appendix for more details).…”

“…In (21), τ BB ′ and σ BB ′ are operators acting in the isospin and in the spin space, respectively. The form of the coupling is derived from the consistency relations of large N c QCD [11,12]; they require not only the degeneracy of the whole tower of states with I = J (nucleon with I = J = 1/2, ∆ with I = J = 3/2, . .…”

“…The obvious tools are various model-independent relations. There is a large class of model-independent constraints based on consistency relations for large N c limit [9][10][11][12][13][14]. Such consistency relations can greatly constrain the chiral behavior associated with the longest distance behavior of the system [4][5][6] provided that it is understood that these relations hold when the large N c limit is taken prior to the chiral limit.…”

Excited Baryons in Large Nc QCD

“…The key idea in the derivation of the symmetry is large N c consistency [ 11,12]. Suppose one were studying pion-nucleon scattering.…”