Signature for Color-Octet Production of $J/\psi$ in $e^+ e^-$ Annihilation

Abstract

The inclusive cross section for the production of $J/\psi$ in $e^+ e^-$ annihilation is studied using a recently developed factorization formalism. In addition to the conventional color-singlet contribution, we include contributions from $c \bar c$ pairs that are produced at short distances in color-octet states. The color-octet contributions are suppressed by the smaller probability for the color-octet $c \bar c$ pair to evolve into a state that includes a $\psi$, but they may dominate near the upper endpoint of the $\psi$ energy spectrum. The signature for the color-octet contribution is a dramatic change in the angular distribution of the $\psi$ near the endpoint.