Theory of hard photoproduction
Michael Klasen
TL;DR
This review synthesizes the theoretical understanding of photons in hard photoproduction, detailing direct and resolved photon interactions as well as virtual and polarized photon processes in photon-photon and photon-hadron collisions. It collects leading and next-to-leading order QCD results in analytic form and surveys jet, hadron, quarkonium, and prompt-photon production with extensive data comparisons from TRISTAN, LEP, and HERA, while also addressing future collider scenarios. The work covers photon spectra from bremsstrahlung, beamstrahlung, and laser backscattering, and discusses how these spectra influence factorization and cross sections in photoproduction. It highlights where pQCD succeeds and where higher-order or non-perturbative effects remain relevant, providing a framework and references for future advances in hard photoproduction theory. Overall, the article serves as a comprehensive state-of-the-art reference for photon-induced processes at high energies and their experimental tests.
Abstract
The present theoretical knowledge about photons and hard photoproduction processes, i.e. the production of jets, light and heavy hadrons, quarkonia, and prompt photons in photon-photon and photon-hadron collisions, is reviewed. Virtual and polarized photons and prompt photon production in hadron collisions are also discussed. The most important leading and next-to-leading order QCD results are compiled in analytic form. A large variety of numerical predictions is compared to data from TRISTAN, LEP, and HERA and extended to future electron and muon colliders. The sources of all relevant results are collected in a rich bibliography.