The baryon vector current in the combined chiral and 1/Nc expansions

TL;DR

This paper calculates the baryon vector current using large-Nc baryon chiral perturbation theory, incorporating loop graphs with octet and decuplet states, and compares predictions with experimental data to validate the approach.

Contribution

It provides a systematic one-loop analysis of the baryon vector current in large-Nc chiral perturbation theory, including SU(3) breaking effects and decuplet-octet mass differences, with comparison to experimental data.

Findings

Large-Nc cancellations occur between different one-loop graphs.

Predictions agree well with experimental data and 1/Nc expansion expectations.

SU(3) flavor symmetry breaking reduces form factors by a few percent.

Abstract

The baryon vector current is computed at one-loop order in large-Nc baryon chiral perturbation theory, where Nc is the number of colors. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference and SU(3) flavor symmetry breaking are accounted for. There are large-Nc cancellations between different one-loop graphs as a consequence of the large-Nc spin-flavor symmetry of QCD baryons. The results are compared against the available experimental data through several fits in order to extract information about the unknown parameters. The large-Nc baryon chiral perturbation theory predictions are in very good agreement both with the expectations from the 1/Nc expansion and with the experimental data. The effect of SU(3) flavor symmetry breaking for the |Delta S|=1 vector current form factors f1(0) results in a reduction by a few percent with respect to the corresponding SU(3) symmetric values.