Measurements of transverse electron scattering from the deuteron in the threshold region at high momentum transfers

Deuteron electrodisintegration cross sections near 180[degree] have been measured near breakup threshold for the four-momentum transfer squared [ital Q][sup 2] range 1.21--2.76 (GeV/[ital c])[sup 2]. Evidence for a change of slope in the cross section near [ital Q][sup 2]=1 (GeV/[ital c])[sup 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 [ital Q][sup 2]. The ratio of inelastic structure functions [ital W][sub 1]([ital Q][sup 2],[ital E][sub [ital n][ital p]])/[ital W][sub 2]([ital Q][sup 2],[ital E][sub [ital n][ital 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 [ital E][sub [ital n][ital p]].