Measuring Color Memory in a Color Glass Condensate at Electron-Ion Colliders

TL;DR

Ball et al. translate the gravitational memory concept into non-Abelian gauge theory by proposing color memory: a color dipole acquires a permanent relative color rotation after passage of color radiation in the Regge limit. They embed this memory in the Color Glass Condensate framework, showing that the memory is encoded in transitions between flat gauge vacua and can be probed through Wilson-line observables and dipole scattering in high-energy DIS. The work connects the memory to the CGC’s classical wee-gluon fields, RG evolution via JIMWLK/BK, and the saturation scale $Q_s$ set by the color-charge density $\mu^2$, outlining how $Q_s$ governs the strength and observational consequences of memory. They propose concrete, clean DIS observables—dipole amplitudes, diffractive and exclusive vector-meson channels—whose strong $Q^2$ and $A$ dependences at a future Electron-Ion Collider would enable decisive tests of color memory in QCD.

Abstract

The color memory effect is the non-abelian gauge theory analog of the gravitational memory effect, in which the passage of color radiation induces a net relative SU(3) color rotation of a pair of nearby quarks. It is proposed that this effect can be measured in the Regge limit of deeply inelastic scattering at electron-ion colliders.