Deuteron electrodisintegration cross sections near 180° have been measured near breakup threshold for the four-momentum transfer squared ${\mathit{Q}}^2$ range 1.21–2.76 (GeV/c${)}^2$. Evidence for a change of slope in the cross section near ${\mathit{Q}}^2$=1 (GeV/c${)}^2$ has been obtained. The data are compared to nonrelativistic calculations, which predict a strong influence of meson-exchange currents. The data are also compared to a hybrid quark-hadron model. None of these calculations agrees with the data over the entire measured range of ${\mathit{Q}}^2$. The ratio of inelastic structure functions ${\mathit{W}}_1$(${\mathit{Q}}^2$,${\mathit{E}}_{\mathit{n}\mathit{p}}$)/${\mathit{W}}_2$(${\mathit{Q}}^2$,${\mathit{E}}_{\mathit{n}\mathit{p}}$) is extracted from the present results and previous forward angle data. No prediction is in good agreement with the deduced ratios at small relative energy ${\mathit{E}}_{\mathit{n}\mathit{p}}$.

• Received 7 October 1992

DOI:https://doi.org/10.1103/PhysRevC.47.1599