Direct, Resonant Production of States with Positive Charge Conjugation in Electron-Positron Annihilation

TL;DR

This paper reviews theoretical predictions for the direct production of positive charge conjugation states in electron-positron annihilation, highlighting model dependence and the significance of production amplitude phases.

Contribution

It provides a comparative analysis of predicted cross sections for specific charmonium states with positive charge conjugation, emphasizing the variability and theoretical uncertainties.

Findings

Predicted cross sections vary significantly between models.

Production of certain states is highly suppressed or negligible.

The phase of the production amplitude critically affects results.

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 $J^{PC} = 1^{++}$ and between 0.16 eV and 4.25 eV for the state with $J^{PC} = 2^{++}$. For the state with $J^{PC} = 0^{++}$ the cross section is of $\cal{O}$ $(m^2_e/M^2_{\chi})$ and thus negligeable for all practical purpose. The importance of the relative phase of the production amplitude is emphasized.