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The proton and deuteron structure functions F p 2 and F d 2 are measured in inelastic muon scattering with an average beam energy of 470 GeV. The data were taken at Fermilab experiment E665 during 1991-92 using liquid hydrogen and deuterium targets. The F2 measurements are reported in the range 0:0008 < x < 0 : 6 and 0:2 < Q 2 < 75 GeV 2. These are the rst precise measurements of F2 in the low x and Q 2 range of the 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 agreement. The E665 data also overlap in x with the HERA data, and there is a smooth connection in Q 2 between the two data sets. At high Q 2 the E665 measurements are consistent with QCDevolved leading twist structure function models. The data are qualitatively described 2 by structure function models incorporating the hadronic nature of the photon at low Q 2. The Q 2 and the W dependence of the data measure the transition in the nature of the photon between a point-like probe at high Q 2 and a hadronic object at low Q 2 .

We have measured the electroproduction of hadrons from nuclei and compare it to the electroproduction from deuterium. We find an attenuation of the forward component which increases with A. The attenuation is less for lower hadronic momenta, but is not a strong function of the other electroproduction variables.In virtual photoproduction of hadrons from nuclei, we have found the first evidence that there is an attenuation of the forward hadrons so produced-the attenuation increasing as the atomic number A increases. However, the average perpendicular momentum with respect to the virtualphoton direction is independent of A. The attenuation effect is similar to the attenuation of largerapidity hadrons produced in neutron-nucleus collisions/The advantages of using virtual photoproduction to study the production and secondary interactions of hadrons in nuclei are twofold. First, the nucleus is, according to present measurements/ transparent to the virtual photon; hence the complications of correcting for the absorption of the incident particle is avoided. Second, a known four-momentum is transferred to the single struck nucleon.This experiment was performed at the Stanford Linear Accelerator Center (SLAG) using a 20.5-GeV/c electron beam incident on a target of liquid hydrogen, liquid deuterium, beryllium, carbon, copper, or tin. As described in more detail elsewhere,^ downstream from the target there were, in this order, an analyzing magnet, an array of multiwire proportional chambers, scintillation counters, lead-Lucite shower counters, and finally a threshold-type, variable-pressure, gas Cherenkov counter. The chamber and counter arrays had an angular acceptance at the target of about ± 200 mrad vertically and + (-•) 33 mrad to + (-) 115 mrad horizontally. The Gherenkov counter covered about one-sixth of this solid angle. The trigger required only a scattered electron with energy greater than 3 GeV, i.e., a pulse corresponding to an electron shower of energy greater than 3 GeV in the shower counter. The accompanying hadrons were detected in the proportional chambers and scintillation counters. Particle identification was made by the Gherenkov counter and by time of flight. In this analysis, the Gherenkov counter information was not used.The targets and their characteristics are listed in Table I. The trigger conditions and all acceptances were the same for all the targets. We also took runs with all targets removed; the yields that we quote have had this measured background subtracted out. The data were corrected for empty target in the case of Hg and D2 (~ 5% sub-TABLE I, Summary of the targets used by type, thickness in grams per square centimeter (Z), thickness in radiation lengths (f), number of incident electrons (n^), and product n^t compared to the same for deuterium. We also list the proton to TT"^ ratio, rp^ in the ^c.m. (proton) range (Ref. 10), -0o4 to 0.0, Element H2 D2

The ratio of cross sections for inelastic muon scattering on xenon and deuterium nuclei was measured at very low Bjorken x (0.00002 < XBJ < 0.25). The data were taken at Fermilab experiment E665 with a 490 GeV/c muon beam incident on liquid deuterium and gaseous xenon targets. Two largely independent analysis techniques gave statistically consistent results. The xenon-to-deuterium per-nucleon cross-section ratio is constant at approximately 0.7 for XBJ below 0.003.

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