Gamma-gamma collider with W_gg < 12 GeV based on the 17.5 GeV SC linac of the European XFEL

TL;DR

This paper proposes a gamma-gamma collider using the European XFEL's existing infrastructure to explore new physics in the 12 GeV mass range, enabling advanced technological development and physics research.

Contribution

It introduces a novel design for a gamma-gamma collider at the European XFEL with minimal disruption, expanding experimental capabilities in high-energy photon interactions.

Findings

Feasibility of adding gamma-gamma collider to XFEL

Potential for studying exotic hadronic states

Development of advanced laser and accelerator technologies

Abstract

We propose and demonstrate that a gamma-gamma collider with W_gg < 12 GeV can be added to the European XFEL with a minimal disruption to its main program. High-energy photons will be obtained by Compton scattering of 0.5 micron laser photons on the existing 17.5 GeV electron beams. Such a gamma-gamma collider would be an excellent place for the development and application of modern technologies: powerful lasers, optical cavities, superconducting linacs, and low-emittance electron sources -- as well as training the next generation of accelerator physicists and engineers. The physics program would include spectroscopy of C=+ resonances in various J^P states b\bar{b}, c\bar{c}, four-quark states, quark molecules and other exotica) in a mass range barely scratched by past and not covered by any current or planned experiments. Variable circular and linear polarizations will help in the determination of quantum numbers and measurement of polarization components of the gamma-gamma cross section (\sigma_\perp, \sigma_\parallel, \sigma_0, \sigma_2).