Inelastic Leptoproduction of J/Psi Mesons at HERA

TL;DR

This paper investigates inelastic J/psi meson production in electron-proton collisions at HERA, measuring cross sections with high precision, comparing them to QCD models, and analyzing meson polarization to understand underlying production mechanisms.

Contribution

It provides high-precision measurements of inelastic J/psi production cross sections and tests non-relativistic QCD models including color octet and singlet contributions.

Findings

Most distributions are well described by the models.

The z distribution shape significantly deviates from data.

J/psi polarization analysis offers insights into production dynamics.

Abstract

The leptoproduction of J/psi mesons is studied in inelastic reactions for four momentum transfers 2<Q^2<100GeV^2. The data were taken with the H1 detector at the electron proton collider HERA and correspond to an integrated luminosity of 77 pb-1. Single differential and double differential cross sections are measured with increased precision compared with previous analyses. New leading order calculations within the non-relativistic QCD factorisation approach including colour octet and colour singlet contributions are compared with the data and are found to give a reasonable description of most distributions. An exception is the shape of the distribution in the J/psi fractional energy, z, which deviates significantly from that of the data. Comparisons with photoproduction are made and the polarisation of the produced J/psi meson is analysed.