J/psi production at the Tevatron and RHIC from s-channel cut

TL;DR

This paper evaluates the s-channel cut contribution to J/psi production, showing it is larger than the traditional color-singlet model estimate and can explain experimental data at Tevatron and RHIC without additional resummation.

Contribution

It introduces a detailed treatment of the s-channel cut contribution using a four-point function constrained by gauge invariance, improving agreement with experimental data.

Findings

s-channel cut contribution is significantly larger than the usual CSM estimate

The model reproduces RHIC data at low transverse momentum without resummation

The approach provides a better understanding of J/psi production mechanisms

Abstract

We report on our recent evaluation of the s-channel cut contribution to J/psi hadroproduction. We show that it is likely significantly larger than the usual cut contribution of the colour-singlet model (CSM), which is known to underestimate the experimental measurements. Here the s-channel cut develops for configurations with off-shell quarks in the bound state. A correct treatment of its contribution requires the introduction of a four point function, partially constrained by gauge invariance and limiting behaviours at small and large momenta. When the unconstrained degrees of freedom are fixed to reproduce the Tevatron data, we show that RHIC data are remarkably well reproduced down to very low transverse momenta P_T without need of resummation of initial-state gluon effects. This unique feature might be typical of s-channel cut contribution.