Quarkonium Production at the Tevatron through Soft Colour Interactions

Abstract

The direct charmonium and bottomonium production rate observed at high-pt in pp-bar collisions at the Tevatron is factors of ten larger than predictions based on conventional perturbative QCD. We show that this excess can be accounted for by our model for soft colour interactions, previously introduced to describe in a novel way the large rapidity gap events observed at HERA.

Figures (2)

• Figure 1: Main pQCD processes for production of a $Q\bar{Q}$ pair in (a) leading order and (b) next-to-leading order.
• Figure 2: Transverse momentum spectra of prompt charmonium $J/\psi , \psi^{\prime}$ and bottomonium $\Upsilon , \Upsilon^{\prime}$ in $p\bar{p}$ collisions at the Tevatron energy. Data from CDF CDF (filled symbols) and DØ D0 (open symbols) compared to results from the soft colour interaction (SCI) model applied to $c\bar{c}$/$b\bar{b}$ production from leading order ($\alpha_s^2$) matrix elements (dashed lines) and with the inclusion of higher order contributions calculated in the parton shower approach (full lines). Production central in pseudorapidity (a) $|\eta|<0.6$, (b) $|y|<0.4$ and forward (c) $2.5<|\eta|<3.7$ (where an assumed 20 % systematic error has been added in quadrature).