Electromagnetism in a gauged chiral model

Abstract

It is shown that the unique addition of electromagnetism to a recently proposed gauged chiral Lagrangian of pseudoscalars and vectors results in the same model as that obtained by the ‘‘hidden symmetry’’ approach. The gauge-invariant treatment of ‘‘vector-meson dominance’’ is essentially equivalent to the old model of Kroll, Lee, and Zumino but we argue for the advantages of working in the ‘‘unusual basis’’ where the photon has zero mass. There is a possible indication that a small calculable deviation from complete vector-meson dominance can close the present gap between experiment and theory for the pion charge radius.