Extraction of the Ratio ${\mathit{F}}_2^{\mathit{n}}/{\mathit{F}}_2^{\mathit{p}}$ from Muon-Deuteron and Muon-Proton Scattering at Small $\mathit{x}$ and ${\mathit{Q}}^2$

The ratio of the deuteron to proton structure functions is measured at very small Bjorken $x$ (down to 1$0^{–6}$) and for $Q^2>0.001\mathrm{}$ Ge${\mathrm{V}}^2$ from scattering of 470 GeV muons on liquid hydrogen and deuterium targets. The ratio $F_2^n{/F}_2^p$ extracted from these measurements is found to be constant, at a value of $0.935\pm 0.008\pm 0.034$, for $x<\mathrm{}0.01\mathrm{}$. This result suggests the presence of nuclear shadowing effects in the deuteron. The dependence of the ratio on $Q^2$ is also examined; no significant variation is found.