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 .

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The ratio of the deuteron to proton structure functions is measured at very small Bjorken x (down to 10 6) and for Q ) 0.001 GeV2 from scattering of 470 GeV muons on liquid hydrogen and deuterium targets. The ratio F2/F2 extracted from these measurements is found to be constant, at a value of

We detected 1 -10 MeV neutrons at laboratory angles from 80 to 140 in coincidence with 470 GeV muons deep inelastically scattered from H, D, C, Ca, and Pb targets. The neutron energy spectrum for Pb can be fitted with two components with temperature parameters of 0.7 and 5.0 MeV. The average neutron multiplicity for 40 ( v~400 GeV is about 5 for Pb, and less than 2 for Ca and C. These data are consistent with a process in which the emitted hadrons do not interact with the rest of the nucleus within distances smaller than the radius of Ca, but do interact within distances on the order of the radius of Pb in the measured kinematic range. For all targets the lack of high nuclear excitation is surprising.PACS numbers: 25.30.MrIn this Letter we present the first measurement of lowenergy neutrons (1 -10 MeV) emitted from a nucleus following deep inelastic scattering (DIS) of a lepton on one of its constituent nucleons. By inferring the excitation energy of the emitting nucleus from these measurements, we provide new information on the response of the nucleus to the momentary color separation that follows DIS. These results are important in understanding a fundamental aspect of QCD, the space-time development of the quark-diquark system resulting from DIS. They are also important for understanding the consequences of quark propagation in nuclear matter in relativistic heavyion reactions.Our present understanding of hadronization, the nonperturbative process by which bare quarks produced in high-energy reactions become hadrons, is largely phenomenological.Several models exist (e.g. , the Lund model [1])which are tuned to the available data and give a good description of the number, flavor, and energy of the created hadrons. However, information on the space-time evolution of hadronization is sparse. Bose-Einstein correlations, which measure coherent effects between identical integral-spin particles, indicate source radii on the order of 2 fm in the rest frame of the source [2]. What is lacking is a clear picture of the distance and time scales required for a bare quark and antiquark, created from the potential 5198 0031-9007/95/74(26)/5198(4)$06. 00