Exclusive Production of Neutral Vector Mesons at the Electron-Proton Collider HERA

TL;DR

This paper reviews five years of experimental results from HERA on vector meson production in high-energy photon-proton interactions, highlighting new insights into energy dependence and production mechanisms.

Contribution

It provides a comprehensive overview of experimental measurements at HERA, comparing them with previous data and discussing theoretical developments in vector meson production.

Findings

Measurements of elastic and inelastic production processes

Energy dependence of cross sections for various vector mesons

Comparison with lower-energy experimental data

Abstract

The first five years of operation of the multi-purpose experiments ZEUS and H1 at the electron-proton storage ring facility HERA have opened a new era in the study of vector-meson production in high-energy photon-proton interactions. The high center-of-mass energy available at this unique accelerator complex allows investigations in hitherto unexplored kinematic regions, providing answers to long-standing questions concerning the energy-dependence of the rho, omega, phi, and J/psi production cross sections. The excellent angular acceptance of these detectors, combined with that of specialized tagging detectors at small production angles, has permitted measurements of elastic and inelastic production processes for both quasi-real photons and those of virtuality exceeding the squared mass of the vector meson. This report provides a quantitative picture of the present status of these studies, comparing them to the extensive measurements in this field at lower energies and summarizing topical developments in theoretical work motivated by the new data.