Fragmentation contribution to quarkonium production in hadron collision

Abstract

We compute the contributions due to gluon and heavy-quark fragmentation to quarkonium production at large transverse momentum in $\bar p p$ and $p p$ collisions. For inclusive $J/\psi$ production, there is a large contribution from the $g \rightarrow \chi_c$ fragmentation. At large $p_T$, this is comparable to the conventional charmonium model prediction via gluon fusion at the ISR and dominates over the latter at the Tevatron energy. This may help to explain, at least partly, the large $J/\psi$ production cross-section recently observed by the CDF experiment. However, the fragmentation contribution to $\psi^{\prime}$ production is not large enough to explain the corresponding CDF data. We also present the results for $\Upsilon$ production at ISR and Tevatron energies.