Color-Octet $J/\psi$ Production at Low $p_{\perp }$

Abstract

We study contributions from color-octet quarkonium formation mechanisms to $J/\psi$ hadroproduction at low $p_{\perp }$. We include transitions of color-octet $c\bar{c}$ states into ``direct'' $J/\psi$ and into ${\chi }_{1,2}$ which decay radiatively into a $J/\psi$. Together with earlier work, this calculation constitutes a complete analysis of $p_{\perp }$-integrated $J/\psi$ production at leading twist. We find that the leading-twist contribution is not sufficient to reproduce the observed production rates and polarization of the $J/\psi$ and ${\chi }_{1,2}$. Hence there must exist other important quarkonium production mechanisms at low $p_{\perp }$.

Comments: REVTEX, 18 pages, 4 figures included