Abstract
The baryon axial vector current is computed in heavy baryon chiral perturbation theory in the large-$N_c$ limit, where $N_c$ is the number of color charges. One-loop nonanalytic corrections of order $m_q \ln m_q$ are comprised in the analysis, with contributions of both intermediate octet and decuplet baryon states, to all orders in the $1/N_c$ expansion of the axial vector current relevant for $N_c=3$. Theoretical expressions are obtained in the limit of vanishing decuplet-octet mass difference only, which allows one to carry out a full comparison with conventional heavy baryon chiral perturbation theory results for three flavors of light quarks and at the physical value $N_c=3$. Both approaches perfectly agree to all orders considered. Furthermore, a numerical analysis via a least-squares fit is performed in order to extract the values of the free parameters of the theory, using the experimental data available. The predictions of formalism are remarkable.
Highlights
The formulation of baryon chiral perturbation theory using an effective Lagrangian for broken SUð3ÞL ×SUð3ÞR chiral symmetry, in which baryons are assumed to be heavy static fermions, was introduced by Jenkins and Manohar three decades ago [1,2]
The formulation, usually referred to as heavy baryon chiral perturbation theory (HBCPT), is a nonrelativistic effective theory that has been proven useful in studying meson-baryon interactions at low energies
The analysis of the baryon axial vector current was one of the earliest applications of HBCPT [1,2], from which two major conclusions were reached: (1) the axial coupling ratios were found to be close to their SUð6Þ values with
Summary
The formulation of baryon chiral perturbation theory using an effective Lagrangian for broken SUð3ÞL ×. [18] include mass [18] to further continue with axial vector current [19,20,21], magnetic moment [22,23], vector current [24], charge radius [25], and more recently s-wave amplitude in nonleptonic decay [26] All these analyses share a common feature: large cancellations occur between one-loop graphs provided that all baryon states in a complete multiplet of the large-N c SUð6Þ spin-flavor. IV the same loop graphs are evaluated within HBCPT; results are arranged in a close parallelism with the ones obtained in the previous section The operator bases used, along with their matrix elements are listed in Appendix D
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