8 research outputs found
The Goldberger-Treiman Discrepancy in SU(3)
The Goldberger-Treiman discrepancy in SU(3) is analyzed in the framework of
heavy baryon chiral perturbation theory (HBChPT). It is shown that the
discrepancy at leading order is entirely given by counterterms from the order
p^3 Lagrangian, and that the first subleading corrections are suppressed by two
powers in the HBChPT expansion. These subleading corrections include meson-loop
contributions as well as counterterms from the order p^5 Lagrangian. Some
one-loop contributions are calculated and found to be small. Using the three
discrepancies (pi-N-N, K-N-Lambda and K-N-Sigma) which can be extracted from
existing experimental data, we find that the HBChPT calculation favors the
smaller g(pi-N-N) values obtained in recent partial wave analyses.Comment: 16 pages,2 figures, revte
The Goldberger-Treiman discrepancy in SU(3)
The Goldberger-Treiman discrepancy in SU(3) is analyzed in the framework of heavy baryon chiral perturbation theory (HBChPT). It is shown that the discrepancy at leading order is entirely given by counterterms from the order p3 Lagrangian, and that the first subleading corrections are suppressed by two powers in the HBChPT expansion. These subleading corrections include meson-loop contributions as well as counterterms from the order p5 Lagrangian. Some one-loop contributions are calculated and found to be small. Using the three discrepancies (ÏNN, KNλ and KNÎŁ) which can be extracted from existing experimental data, the authors find that the HBChPT calculation favors the smaller g(ÏNN) values obtained in recent partial wave analyses.Facultad de Ciencias Exacta
Masses of Orbitally Excited Baryons in Large N_c QCD
We present the first phenomenological study of the masses of orbitally
excited baryons in large N_c QCD. Restricting here to the nonstrange sector of
the L=1 baryons, the 1/N_c expansion is used to order and select a basis of
effective operators that spans the nine observables (seven masses and two
mixing angles). Fits are performed using subsets of the complete set of nine
operators, including corrections up to O(1/N_c) where leading order is N_c^1.
This study shows that the 1/N_c expansion provides an excellent framework for
analyzing the mass spectrum, and uncovers a new hierarchy of operator
contributions.Comment: 15 pages, revte
Operator Analysis of L=1 Baryon Masses in Large N_c QCD
We consider in detail the mass operator analysis for the nonstrange L=1
excited baryons in large N_c QCD. We present a straightforward procedure for
constructing the large N_c baryon wavefunctions, and provide complete analytic
expressions for the matrix elements of all the independent isosinglet mass
operators. We discuss the relationship between the old-fashioned operator
analyses based on nonrelativistic SU(6) symmetry and the modern large N_c
approach, which has a firmer theoretical foundation. We then suggest a possible
dynamical interpretation for the subset of operators preferred strongly by the
data.Comment: 36 pages LaTe