Charm-pair Rescattering Mechanism for Charmonium Production in High-energy Collisions

TL;DR

This paper investigates the charm-pair rescattering mechanism for charmonium production, finding it contributes but is not the dominant process at high energies, and provides a calculation within the NRQCD framework.

Contribution

The paper identifies the charm-pair rescattering as a next-to-next-to-leading order contribution in NRQCD and calculates its impact on J/psi production at the Tevatron.

Findings

Rescattering contribution competes with leading-order color-singlet term at high transverse momentum.

Rescattering is significantly smaller than next-to-leading-order contributions.

Charm-pair rescattering is not the primary mechanism for charmonium production.

Abstract

A new mechanism for heavy quarkonium production in high-energy collisions called the "s-channel cut" was proposed in 2005 by Lansberg, Cudell, and Kalinovsky. We identify this mechanism physically as the production of a heavy quark and anti-quark that are on-shell followed by their rescattering to produce heavy quarkonium. We point out that in the NRQCD factorization formalism this rescattering mechanism is a contribution to the color-singlet model term at next-to-next-to-leading order in perturbation theory. Its leading contribution to the production rate can be calculated without introducing any additional phenomenological parameters. We calculate the charm-pair rescattering (or s-channel cut) contribution to the production of J/psi at the Tevatron and compare it to estimates by Lansberg et al. using phenomenological models. This contribution competes with the leading-order term in the color-singlet model at large transverse momentum but is significantly smaller than the next-to-leading-order term. We conclude that charm-pair rescattering is not a dominant mechanism for charmonium production in high-energy collisions.