Diffractive photoproduction of Upsilon states at HERA

TL;DR

This paper presents theoretical predictions for the diffractive photoproduction cross sections of Upsilon states at HERA, incorporating novel effects like skewed kinematics and real amplitude contributions, aligning well with recent experimental data.

Contribution

It introduces a refined theoretical framework including skewed kinematics and real part effects, predicting a stronger energy dependence than J/Psi production.

Findings

Predicted cross sections agree with ZEUS and H1 data.

Significant enhancement due to skewed kinematics and real amplitude.

Stronger energy rise than in J/Psi production.

Abstract

Cross sections for the diffractive photoproduction of the Upsilon-family at HERA energies, within the framework of the analysis by Frankfurt, Koepf and Strikman, are presented. They compare well with the recent preliminary data from ZEUS and H1. Two novel effects lead to a significant enhancement of the original calculation: the non-diagonal (or skewed) kinematics, calculated to leading-log(Q^2) accuracy, and the large magnitude of the real part of the amplitude. A considerably stronger rise in energy is predicted than that found in J/Psi-production.