Inclusive production of η′ (958) and f_o (975) mesons in the υ energy region

The inclusive production cross sections of η′ (958) and f_o (975) mesons are measured in e⁺e^- annihilation in the nonresonant continuum around {Mathematical expression} GeV and in decays of the υ resonances using the ARGUS detector. For η′ (958) mesons, a production ratio of η′ (958)/η_dir=0.35±0.24, with η_dir=η-BR(η′→ηX)·η′, is determined in direct υ(1 S) decays, which can be partially explained by the pseudoscalar singlet/octet mixing. For f_o(975) production, we obtain a production ratio of f_o(975)/p(770)°=0.17±0.030 in direct υ(1 S) decays. In its production features, the f_o(975) behaves like an ordinary meson, though a K {Mathematical expression} molecule nature cannot be excluded. The substantial production yield of the f_o(975) meson demonstrates the important effect of feeddown from mesons beyond the basic multiples on pseudoscalar and vector meson production.