Heavy ion beam loss mechanisms at an electron-ion collider

TL;DR

This paper calculates cross-sections for key processes affecting heavy-ion beam stability at electron-ion colliders, highlighting their impact on luminosity and detector backgrounds.

Contribution

It provides the first detailed calculations of bound-free pair production and Coulomb excitation cross-sections relevant for collider operation with heavy nuclei.

Findings

Large cross-sections (28-56 mb) for bound-free pair production and Coulomb excitation.

Beam losses due to these processes limit achievable luminosity.

Production of neutrons impacts detector backgrounds.

Abstract

There are currently several proposals to build a high-luminosity electron-ion collider, to study the spin structure of matter and measure parton densities in heavy nuclei, and to search for gluon saturation and new phenomena like the colored glass condensate. These measurements require operation with heavy-nuclei. We calculate the cross-sections for two important processes that will affect accelerator and detector operations: bound-free pair production, and Coulomb excitation of the nuclei. Both of these reactions have large cross-sections, 28-56 mb, which can lead to beam ion losses, produce beams of particles with altered charge:mass ratio, and produce a large flux of neutrons in zero degree calorimeters. The loss of beam particles limits the sustainable electron-ion luminosity to levels of several times $10^{32}/$cm$^2$/s.