Color-Octet ${\psi }^{\prime }$ Production at Low $p_{\perp }$

Abstract

We study contributions from color-octet quarkonium formation mechanisms to $p_{\perp }$-integrated ${\psi }^{\prime }$ production cross sections in pion-nucleon reactions. The observed polarization of the ${\psi }^{\prime }$ is not reproduced by the lowest-order leading-twist color-singlet and color-octet mechanisms. This suggests that there are important quarkonium production mechanisms beyond leading twist.

Comments: 9 pages