Prompt J/psi production at e^+e^- colliders

TL;DR

The study analyzes prompt $J/\psi$ production at $e^+e^-$ colliders within NRQCD, contrasting color-singlet and color-octet mechanisms across energy scales. It finds color-octet channels overwhelmingly dominate singlet contributions, with distinct energy dependences and characteristic $J/\psi$ energy spectra for the two octet processes. The work also discusses strategies to extract color-octet matrix elements from $e^+e^-$ data at different energies, offering cleaner tests of NRQCD than hadroproduction. It highlights potential for precise NRQCD scaling tests and notes the need to incorporate $Z^0$ effects at high energies in future analyses.

Abstract

In this paper, we discuss the prompt j/psi production at e^+e^- colliders via color-singlet and color-octet production mechanisms. The color-singlet production processes include 1) e^+e^- to J/ψgg; 2) e^+e^- to J/ψc\bar{c}; 3) e^+e^- to q \bar q ggJ/ψand e^+e^- to q \bar q gχ_c followed by χ_c to J/ψγ. The color-octet production processes include 1) e^+e^- to J/ψg; 2) e^+e^- to j/psi q\bar q. Of all these production channels, we find that the color-octet contributions dominate over the color-singlet contributions at any energy scales. At low energies (\sqrt{s}< 20 GeV), the dominant channel is e^+e^- to J/ψg whereas at high energies e+e^- to j/psi q\bar q will take the leading part. We also find that the energy spectrum for the color-octet j/psi production in process e^+e^- to j/psi q\bar q is very soft, and the mean energy of the produced j/psi is only about 10 GeV~ 20 GeV even at very high energies (e.g. at 1000 GeV). The extraction of color-octet matrix elements from j/psi production in e^+e^- collisions is also discussed.