  The event generator BEEC [Z. Yang, X.G. Wu and X.Y. Wang, Comput. Phys.
Commun. 184, 2848 (2013)] was devoted to the simulation of heavy quarkonium
production at an unpolarized electron-positron collider. We upgraded it here by
adding the generation of quarkonium with polarized electron and positron beams.
In addition, the production of color-singlet 2S-wave states were included.
Several future electron-positron colliders with high luminosity have been under
discussion in the past decade. Especially, their possibility of producing
polarized beams is important for providing more insights into the underlying
physics. This upgraded version offers a useful tool for the feasibility study
on quarkonium from the experimental side.
