Hadroproduction of Charmonium at Large $x_F$

Abstract

We present a higher-twist production mechanism for ${\eta }_c$ and ${\chi }_J$ charmonium at large momentum fraction $x_F$ in pion-nucleon collisions. The higher-twist contribution is essentially independent of $x_F$ and therefore becomes dominant at large $x_F$, where the leading-twist contribution falls off as $(1-x_F{)}^3$. We show that the higher-twist mechanism produces longitudinally polarized ${\chi }_1$ and ${\chi }_2$. For the ${\chi }_2$, this is clearly different from the leading-twist prediction of transverse polarization. For the ${\chi }_1$, the polarization of the leading- and higher-twist contributions is qualitatively similar.

Comments: 14 pages, standard Latex, 3 figures included as an uuencoded Postscript file