Proton and deuteron structure functions in muon scattering at 470-GeV

The proton and deuteron structure functions F{sub 2}{sup p} and F{sub 2}{sup d} measured in inelastic muon scattering with an average beam energy of 470 GeV. The data were taken at Fermilab experiment 665 during 1991-1992 using liquid hydrogen and deuterium targets. The F{sub 2} measurements are reported in the range 0.0008 < x < 0.6 and 0.2 < Q{sup 2} < 75 GeV{sup 2}. These are the first precise measurements of F{sub 2} in the low x and Q{sub 2} range of the data. The E665 data overlap in x with the HERA data, and there is a smooth connection in Q{sup 2} between the two data sets. At high Q{sup 2} the E665 measurements are consistent with QCD-evolved leading twist structure function models. The data are qualitatively described by structure function models incorporating the hadronic nature of the photon at low Q{sup 2}. The Q{sup 2} and the W dependence of the data measure the transition in the nature of the photon between a point-probe at high Q{sup 2} and a hadronic object at low Q{sup 2}.