PROTON AND DEUTERON STRUCTURE FUNCTIONS IN MUON SCATTERING AT 470 GEV

The proton and deuteron structure functions F-2(p) and F-2(d) are meas ured in inelastic muon scattering with an average beam energy of 470 G eV. The data were taken at Fermilab experiment E665 during 1991 and 19 92 using liquid hydrogen and deuterium targets. The F-2 measurements a re reported in the range 0.0008<x<0.6 and 0.2<Q(2)<75 GeV2. These are the first precise measurements of F-2 in the low x and Q(2) range of t he data. In the high x range of the data where they overlap in x and Q (2) with the measurements from NMC, the two measurements are in agreem ent. The E665 data also overlap in x with the DESY HERA data, and ther e is a smooth connection in Q(2) between the two data sets. At high Q( 2) the E665 measurements are consistent with QCD-evolved leading twist structure function models. The data are qualitatively described by st ructure function models incorporating the hadronic nature of the photo n at low Q(2). The Q(2) and the W dependence of the data measure the t ransition in the nature of the photon between a pointlike probe at hig h Q(2) and a hadronic object at low Q(2).