Perturbative QCD Analysis of Near Threshold Heavy Quarkonium Photoproduction at Large Momentum Transfer

TL;DR

This paper uses perturbative QCD to analyze near-threshold heavy quarkonium photoproduction at large momentum transfer, revealing a dominant three-quark state with nonzero orbital angular momentum and a specific power-law behavior.

Contribution

It demonstrates a modified power counting approach and identifies the dominant Fock state in near-threshold production, impacting experimental interpretation.

Findings

The differential cross section scales as 1/(-t)^5.

The three-quark Fock state with orbital angular momentum dominates.

Results influence the understanding of gluonic gravitational form factors.

Abstract

We apply perturbative QCD to investigate the near threshold heavy quarkonium photoproduction at large momentum transfer. From an explicit calculation, we show that the conventional power counting method will be modified and the three quark Fock state with nonzero orbital angular momentum dominates the near threshold production. It carries a power behavior of $1/(-t)^5$ for the differential cross section. We further comment on the impact of our results on the interpretation of the experiment measurement in terms of the gluonic gravitational form factors of the proton.