The uncertainties of the gluon's helicity contribution delta G versus the quark helicity contribution to the proton spin from the region of parton momentum fractions x > 0.001 that would be achieved by the EIC for different center-of-mass energies.

Alberto Accardi et al, Electron Ion Collider: The Next QCD Frontier - Understanding the glue that binds us all, arXiv:1212.1701