"Power" vs "radius" models of form factors: Decay characteristics

Abstract

We present a detailed study of the relative performance of two classes of phenomenological form factors, the "power" form factor (PFF) and the "radius" form factor (RFF), in the understanding of pseudoscalar decays of a large number of experimentally known baryon and meson resonances in both ($L\ifmmode\pm\else\textpm\fi{}1$) waves. The PFF which turns out to work best is essentially characterized by the division of each 4-momentum (in the multiple momentum couplings) by the c.m. energy of the daughter baryon and daughter meson for the ($L\ifmmode\pm\else\textpm\fi{}1$) waves, respectively. For the RFF we use two versions, one employed by the Particle Data Group and another proposed by us to incorporate certain features of the Harari radius model. Both sets provide a consistent pattern for ($L+1$)-wave decays compatible with the universality of reduced coupling constants for Regge and exchange-degenerate partners. For the ($L\ensuremath{-}1$)-wave decays, the PFF has an edge over the RFF because of its flexibility to incorporate the Gell-Mann, Oakes, and Renner effect. It is also pointed out that reaction processes as well as electromagnetic mass differences (considered in separate papers) can discriminate between the two forms, considerably favoring PFF over the RFF.