The diiractive production of 0 (770) mesons in muon-proton interactions is studied in the kinematic region 0.15 GeV 2 < Q 2 < 20 GeV 2 and 20 GeV < < 420 GeV. The data were obtained in the Fermilab xed-target experiment E665 with primary muons of 470 GeV energy. Results are presented on the Q 2 , x and dependence of the cross section, on the shape of the + ? mass spectrum, on the slope of the diiraction peak and on the production and decay angular distributions of the 0 (770). The cross section for diiractive production of 0 by virtual photons on protons depends mainly on Q 2. At xed Q 2 , no signiicant dependence on x or is observed. The extrapolation to Q 2 = 0 yields a photoproduction cross section of (10:30 0:33) b. The slope of the t 0 distribution has a value of (7:00:2) GeV ?2 , with a tendency to decrease as Q 2 increases. The production and decay angular distributions of the 0 depend strongly on Q 2 and are consistent with s-channel helicity conservation. The ratio R = L == T deduced from the decay angular distributions rises strongly with Q 2 , passing the value of 1 at Q 2 2 GeV 2 .

The diffractive production of ρ0(770 @#@) mesons in muon-proton interactions is studied in the kinematic region 0.15 GeV2 < Q2 < 20 GeV2 and 20 GeV < ? < 420 GeV. The data were obtained in the Fermilab fixed-target experiment E665 with primary muons of 470 GeV energy. Results are presented on the Q2, x and ? dependence of the cross section, on the shape of the ρ+ρt - mass spectrum, on the slope of the diffraction peak and on the production and decay angular distributions of the ρ0(770). The cross section for diffractive production of ρ0 by virtual photons on protons depends mainly on Q2. At fixed Q2, no significant dependence on x or ? is observed. The extrapolation to Q2 = 0 yields a photoproduction cross section of (10.30 ± 0.33) μb. The slope of the t′ distribution has a value of (7.0 ± 0.2) GeV−2, with a tendency to decrease as Q2 increases. The production and decay angular distributions of the ρ0 depend strongly on Q2 and are consistent with s-channel helicity conservation. The ratio R = σ l /σ t deduced from the decay angular distributions rises strongly with Q2, passing the value of 1 at Q2 ≈ 2 GeV2.

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}.

The ratio of the deuteron to proton structure functions is measured at very small Bjorken $x$ (down to 1${0}^{--6}$) and for ${Q}^{2}>0.001$ Ge${\mathrm{V}}^{2}$ from scattering of 470 GeV muons on liquid hydrogen and deuterium targets. The ratio ${F}_{2}^{n}{/F}_{2}^{p}$ extracted from these measurements is found to be constant, at a value of $0.935\ifmmode\pm\else\textpm\fi{}0.008\ifmmode\pm\else\textpm\fi{}0.034$, for $x<0.01$. This result suggests the presence of nuclear shadowing effects in the deuteron. The dependence of the ratio on ${Q}^{2}$ is also examined; no significant variation is found.

Nuclear shadowing is observed in the per-nucleon cross sections of positive muons on carbon, calcium and lead as compared to deuterium. The data were taken by Fermilab experiment E665 using inelastically scattered muons of mean incident momentum 470 GeV/c. Cross-section ratios are presented in the kinematic region 0.0001<x Bj <0.56 and 0.1<Q2<80 GeV2. The data are consistent with no significant ν orQ2 dependence at fixedx Bj . Asx Bj decreases, the size of the shadowing effect, as well as itsA dependence, are found to approach the corresponding measurements in photoproduction.