Pion Electroproduction Amplitude Relations in the 1/N_c Expansion

TL;DR

This paper derives relations between pion electroproduction amplitudes using the 1/N_c expansion of QCD, providing theoretical predictions that compare favorably with experimental data, especially at leading order.

Contribution

It introduces linear relations between electromagnetic multipole amplitudes in pion electroproduction derived from the 1/N_c expansion, including both leading and next-to-leading order effects.

Findings

Leading-order relations agree well with data away from resonances.

Next-to-leading-order relations offer limited improvement.

The approach provides a systematic QCD-based framework for amplitude relations.

Abstract

We derive expressions for pion electroproduction amplitudes in the 1/N_c expansion of QCD, and obtain from them linear relations between the electromagnetic multipole amplitudes that hold at all energies. The leading-order relations in 1/N_c compare favorably with available data (especially away from resonances), but the next-to-leading-order relations tend to provide only small or no improvement.