Direct, resonant production of states with positive charge conjugation in electron-positron annihilation

Abstract

Recent theory results on direct production of resonances with positive charge conjugation in electron-positron annihilation are reviewed. The strong model dependence is emphasized, with predictions varying between 0.03 eV and 0.43 eV for the charmonium state with JPC = 1++ and between 0.16 eV and 4.25 eV for the state with JPC = 2++. For the state with JPC = 0++ the cross section is of O (m2 e/M2 χ) and thus negligeable for all practical purpose. The importance of the relative phase of the production amplitude is emphasized.