Understanding η'→ηππ and allied processes despite adler zeros

Abstract

With use of the (hitherto obscure) negative-parity meson matrix N₊ of partial symmetry, an η'→ηππ amplitude, explicitly satisfying the Adler conditions, has been constructed within the relativistic quark pair-creation model without any adjustable parameters. The model yields a total η' width of 388 keV and ηππ, ρ⁰γ, and γγ branching ratios of 68.0%, 29.9%, and 1.88%, all in excellent agreement with data. The same model gives the π-π scattering lengths as m_πa₀=0.19, m_πa₂=0.08.