Saturation of shadowing at very low Bjorken<i>x</i>

The ratio of cross sections for inelastic muon scattering on xenon and deuterium nuclei was measured at very low Bjorken x (0.000 02${\mathit{x}}_{\mathrm{Bj}}$0.25). The data were taken at Fermilab experiment E-665 with a 490 GeV/c muon beam incident on liquid deuterium and gaseous xenon targets. Two largely independent analysis techniques gave statistically consistent results. The xenon-to-deterium per-nucleon cross-section ratio is constant at approximately 0.7 for ${\mathit{x}}_{\mathrm{Bj}}$ below 0.003.