Inelastic Production of J/psi Mesons in Photoproduction and Deep Inelastic Scattering at HERA

TL;DR

This paper reports measurements of inelastic J/psi meson production in ep scattering at HERA, comparing experimental data with theoretical models to evaluate their accuracy in describing the process.

Contribution

It provides new measurements of inelastic J/psi production cross sections and helicity distributions, and compares these with predictions from colour singlet and non-relativistic QCD models.

Findings

Colour singlet model with k_T factorisation describes data well.

Collinear NLO calculations underestimate the data.

Helicity distributions are analyzed and compared to models.

Abstract

A measurement is presented of inelastic photo- and electroproduction of J/psi mesons in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and the helicity distributions of the J/psi mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using a k_T factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.