Gamma N Delta Form Factors and Wigner Rotations

TL;DR

This paper discusses the importance of Wigner rotations in the analysis of Delta N gamma form factors, highlighting potential issues in previous studies that used the Jones-Scadron parametrization without accounting for these rotations.

Contribution

It identifies the oversight of Wigner rotations in the common Delta N gamma form factor analysis and emphasizes their significance when the Delta is not at rest.

Findings

Wigner rotations cause helicity mixing in Delta N gamma form factors.

Many previous studies may have overlooked these rotations, affecting their results.

The paper suggests incorporating Wigner rotations for accurate form factor analysis.

Abstract

For more than 50 years the Delta N gamma form factors have been studied experimentally, theoretically, and phenomenologically. Although there has been substantial progress in understanding their behavior, there remains much work to be done. A major tool used in many investigations is the Jones-Scadron Delta rest frame parametrization of the three Delta N gamma form factors. We point out that many studies utilizing this parametrization may not account for Wigner rotations and the consequent helicity mixing that ensues when the Delta is not at rest.