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Experimental results are presented on the scattering of 250-MeV electrons by ${\mathrm{Ca}}^{40}$, ${\mathrm{Ca}}^{42}$, ${\mathrm{Ca}}^{44}$, ${\mathrm{Ca}}^{48}$, and ${\mathrm{Ti}}^{48}$, and of 500-MeV electrons by ${\mathrm{Ca}}^{40}$ and ${\mathrm{Ca}}^{48}$. An analysis is made in terms of a phenomenological three-parameter shape, and a new, more accurate charge distribution is obtained for ${\mathrm{Ca}}^{40}$. The experiments also lead to a detailed exploration of the radial dependence of the differences in charge distributions of the various isotopes. Implications for nuclear theory are discussed. Comparison is made with the results of other electron scattering and of muonic x-ray experiments. The latter comparison permits an independent determination of an upper limit on the muon electromagnetic radius ${{〈{r}^{2}〉}_{\ensuremath{\mu}}}^{\frac{1}{2}}\ensuremath{\lesssim}0.35$ F.

Elastic electron scattering cross sections have been measured for 6Li at 500 MeV and values of q sup 2, the momentum transfer squared, up to 13 f(m sup (-2)). Calculations including nucleon-nucleon correlations predict a diffraction minimum beyond the range of previous measurements for 6Li. The results for 6Li do show a diffraction minimum at q sup 2 = 8 f(m sup (-2)); they are also compared with a phase shift calculation using an empirical charge distribution. (Author)

The electromagnetic structure of the ${\mathrm{He}}^{3}$ nucleus has been investigated by means of high-energy electron scattering. A separation of the charge and magnetic form factors has been accomplished. The charge form-factor data extend to ${q}^{2}=20$ ${\mathrm{fm}}^{\ensuremath{-}2}$ and exhibit a diffraction minimum at ${q}^{2}=11.6$ ${\mathrm{fm}}^{\ensuremath{-}2}$; the magnetic scattering is measured to ${q}^{2}=12.5$ ${\mathrm{fm}}^{\ensuremath{-}2}$. The results are discussed in terms of models for the charge and magnetic distributions of the nucleus.

The differential scattering cross sections have been measured for electron scattering from randomly oriented and aligned Ho165 nuclei. The alignment axis was parallel to the direction of the momentum transferred to the nucleus. Incident electron energies from 160.6 MeV to 462.2 MeV were used at a fixed polar scattering angle of 36 degrees. Available theories are unable to explain the measured difference between the aligned and non-aligned cross sections. (Author)

We have measured the cross section for elastic electron scattering from ${\mathrm{He}}^{4}$ at values of ${q}^{2}$, the four-momentum transfer squared, ranging from 0.5 to 20.0 ${\mathrm{F}}^{\ensuremath{-}2}$. Previous Stanford measurements extended up to ${q}^{2}=6.2$ ${\mathrm{F}}^{\ensuremath{-}2}$ and were consistent with a Gaussian shape for the charge distribution of the ${\mathrm{He}}^{4}$ nucleus. Our results confirm the earlier data but show a deviation from the Gaussian model for ${q}^{2}g6$ ${\mathrm{F}}^{\ensuremath{-}2}$. At ${q}^{2}=10$ we observe a diffraction minimum of the scattering cross section. Among the models which have been found to fit the new data is the Fermi three-parameter charge distribution. The rms radius ${〈{r}^{2}〉}^{\frac{1}{2}}$, the half-density radius ${r}_{\frac{1}{2}}$, and the 90% to 10% skin thickness $t$ of the charge distribution have been calculated for the models which adequately fit the data. The results indicate that the surface of the ${\mathrm{He}}^{4}$ charge distribution is less diffuse than implied by the nuclear harmonic-oscillator model.

The spectra of electrons scattered inelastically from 4 He have been measured at incident energies from 150 MeV to 400 MeV for scattering angles from 38° to 90°. Through the use of a liquid 4 He target, a high momentum resolution (≈0.25%) was obtained, and the 20 MeV 0 + state of the α-particle was observed for the first time in electron scattering. The excitation energy and the total width of this state were determined and are in good agreement with the results from other experimental methods. It was found that the total disintegration cross section appears be smaller than 2(σ p +σ n ) by more than an order of magnitude at the lowest q 2 (≈ 0.33 fm −2 ). In earlier work the assumption of a total cross section of 2(σ p +σ n ) was found to be quite accurate for higher q 2 . As a new result, the partial radiative width for the 0 + state is determined to be Γ rad = 1.1±0.3 meV.

The mirror nuclei of tritium and helium-3 have been studied by the method of elastic electron scattering. Absolute cross sections have been measured for incident electron energies in the range 110-680 MeV at scattering angles lying between 40 and 135\ifmmode^\circ\else\textdegree\fi{} in this energy range. The data have been interpreted in a straightforward manner and form factors are given for the distributions of charge and magnetic moment in the two nuclei over a range of four-momentum transfer squared 1.0-8.0 ${\mathrm{F}}^{\ensuremath{-}2}$. Model-independent radii of the charge and magnetic-moment distributions are given and an attempt is made to deduce form factors describing the spatial distribution of the protons in tritium and helium-3.

The study of electrons scattered inelastically from the deuteron has been extended to 600 Mev. Data at 500 Mev were reported in an earlier paper. Results are presented for seven scattering angles between 45\ifmmode^\circ\else\textdegree\fi{} and 135\ifmmode^\circ\else\textdegree\fi{}. A comparison of the deuteron's cross section at these angles with the corresponding free proton cross sections permits a determination of the form factor associated with the magnetic moment distribution of the neutron. Two different methods of analyzing the data are described, and the rms radius of the neutron for an exponential density distribution of the magnetic cloud can be shown to lie between the limits of 0.75\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm and 0.95\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm. The rms radius of the neutron may be taken to be (0.80\ifmmode\pm\else\textpm\fi{}0.10)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm and is very close to the value found for an exponential model of the magnetic cloud in the proton.

New information is reported on differences between the charge distributions of Ca40 and of Ca44, obtained by means of elastic scattering of 250 MeV electrons. Attention is focused, experimentally and theoretically, on the difference in scattering between the two isotopes.

Data on elastic electron-deuteron scattering is obtained using a two-spectrometer coincidence-detection technique. Preliminary analysis of the data has been compared with an impulse approximation theory and has enabled the investigation of possible meson-exchange and/or relativistic effects. The measurements were made using a 1.2 cm thick liquid deuterium target and two 180 degree N=1/2, double-focusing magnetic spectrometers. Deuterons were deflected by a 72-inch, 100 MeV/c spectrometer and detected by a six-channel ladder of plastic scintillators. Electrons were deflected by a 36-inch, 550 MeV/c spectrometer and detected by a similar five-channel ladder with a liquid Cerenkov backing counter. The solid angle was defined by the 36-inch spectrometer. By demanding a coincidence between counts from each spectrometer, background events from competing inelastic processes were eliminated. De3ayed accidental coincidence rates were monitored. (Author)

The absolute elastic electron-scattering cross sections of Ca/sup 40/, V/ sup 51/, Co/sup 59/ In/sup 115/ Sb/sup 121//sup / ,>s/sup 123/,and Bi/sup 209/ were measured at a number of angles at a primary electron energy of 183 Mev. The cross sections were obtained by comparison with scattering from the proton. The data were compared with the previous relative angular distributions of Hahn, Ravenhall, and Hofstadter. The present data are in closer agreement with the charge distributions found from fitting a Fermi two-parameter model to the older data than with those found from a fit of the Ford and Hill charge distributions. The absolute cross sections for Bi/sup 209/ show the least agreement: they are 35% larger than the predictions of the Fermi model and about 70% larger than the Ford and Hill model. (auth)

High-energy electron scattering measurements have demonstrated clearly the existence of deviations from point-nucleon scattering laws. The results obtained in the proton and neutron investigations have been interpreted as evidence of the finite sizes of the nucleons. The results already established as well as some of the most recent findings of the electron-scattering method are summarized. A brief account of the significance of the observed deviations from point-nucleon scattering is presented. (W.D.M.)

The doubly-magic nucleus of Ca(40) has been investigated by the electron scattering technique at an incident energy of 250 MeV. The elastic scattering behavior has been resolved from the inelastic scattering and absolute data on cross sections have been obtained for both types of events. In the case of the elastic scattering the first and second diffraction features have been observed and measured. It has been possible to make a comparison of the elastic data with theoretical calculations based on a phase shift analysis for certain assumed models of the nuclear charge density distribution. The combination of such an analysis with the present data, and also with earlier data on the same nucleus, permits the determination of the radius and skin thickness of the Ca(40) nucleus with a precision greater than has been attainable heretofore. An investigation of the dependence of the density distribution on a third parameter indicates that a Fermi distribution, or models close to this type, are required to fit the experimental data. A Fermi radial charge density distribution with radius c =3.60 F, and skin thickness t = 2.50 F fits the data extremely well. (Author)

Electron scattering from the bound neutron and proton in the deuteron has been studied at various scattering angles between 75\ifmmode^\circ\else\textdegree\fi{} and 135\ifmmode^\circ\else\textdegree\fi{} for 500-Mev and 600-Mev electrons. A comparison of these scattering cross sections with those of the free proton permits a determination of the density distribution of the magnetic cloud around the neutron. By using theories developed by Jankus and Blankenbecler, the root-mean-square radius of the neutron is shown to lie between the limits 0.80\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm and 0.90\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm. The choice between these radii depends on whether the deuteron total cross sections or differential (peak) cross sections are compared with the protonic scattering cross section. Since presently available theory has not yet developed sufficiently to decide definitely between these possibilities, the root-mean-square size may be taken to be (0.85\ifmmode\pm\else\textpm\fi{}0.10)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm with small error. The neutron's magnetic cloud clearly does not have the small size obtained by measurement of its charge cloud from experiments on the neutron-electron interaction, and this anomaly challenges the present concepts of nucleon size.

The long-standing discrepancies between theory and experiment in the magnetic elastic and inelastic scattering of electrons from the deuteron at high momentum transfer are reexamined. It is concluded that the predictions using most deuteron models agree with the elastic scattering data if one employs the presently accepted dipole fit (with scaling) for the proton and neutron form factors. A second conclusion is that the inelastic scattering to the $^{1}S_{0}$ state is not affected by small changes in the nucleon form factors, but is completely dominated by dynamic effects such as those due to meson-exchange diagrams.

Previous measurements of the transition probabilities for low-energy excitations in 12 C, using high-energy electron scattering techniques, required considerable extrapolation of the data to obtain the desired results. The present paper reports the results of new data obtained at lower values of momentum transferred to the nucleus. Transition widths for the three lowest-energy excited states in 12 C are determined using the new data. The results of the experiment allow a much greater confidence in the method employed in this study for determining transition widths.

Measurements of average separation energies and of Fermi momenta for40Ca and48Ca are reported. Evidence for the possible existence of “bump” structure in the quasi-elastic scattering of electrons from48Ca is also presented.

We have studied elastic electron scattering from 4He at values of q2, the momentum transfers squared. ranging from 0.5 fm−2 to 10.0 fm−2. Among the models which have been found to fit the new data is modified Gaussian distribution with a half density radius of 1.19 fm and a skin thickness of 1.61 fm.

Distributions of electrons elastically scattered by He/sup 3/ and T are compared in order to analyze the three-body forces acting in these mirror nuclei. The charge and magnetic form factors for the nuclei are calculated. Three of these form factors are nearly equal to one another but the charge form factor of He/sup 3/ is different from the other three. (T.F.H.)

We have searched for virtual excited states of 3 He by inelastic electron scattering at E = 200 MeV and θ = 60°. No evidence for narrow states excited with cross section greater than 3 × 10 −33 cm 2 /sr has been found for excitation energies up to 17 MeV.

High momentum transfer elastic electron scattering data (q = 0.8 – 3.7 fm−1) from 24Mg, 28Si and S are presented and analysed with phenomenological charge distributions ϱ(r); and oscillation in ϱ(r) due to shell-model structure is obtained. An analysis in terms of a Woods-Saxon potential is described and the 2s-1d occupation numbers are deduced.

The authors propose to measure the inclusive deep inelastic electron-nucleon scattering cross sections on hydrogen and deuterium. Cross sections will be measured in the range of momentum transfers Q{sub min}{sup 2} = 0.160 (GeV/c){sup 2} and Q{sub max}{sup 2} = 160.0 (GeV/c){sup 2}, in the range of recoil hadronic mass squared of W{sub min}{sup 2} = 2 GeV{sup 2} and W{sub max}{sup 2} = 450 GeV{sup 2}. The electromagnetic structure functions, {nu}W{sub 2}(Q{sup 2},{nu}) and W{sub 1}(Q{sup 2},{nu}), of both protons and neutrons will be measured and separated by well-known methods, in the highest possible unexplored FERMILAB kinematical regions. The high intensity Proton-West superconducting beam will be used to yield an electron beam of high purity, based on a synchrotron radiation compensated tuning technique. The electron beam will be used at 150 GeV (5 x 10{sup 8} e{sup {+-}}/pulse), at 175 GeV (3.6 x 10{sup 8} e{sup {+-}}/pulse) and at 250 GeV (1 x 10{sup 8} e{sup {+-}}/pulse). The scattered electron will be detected with good acceptance, good resolution and excellent identification. The detector will be the E-192 apparatus with small additions. A simple self-calibration procedure is available, both in experiment and apparatus, removing beam-associated and target-associated background in themore » entire (Q{sup 2}, W{sup 2}) kinematical regions. Usually, interesting physics occurs where counting rates are small. This experiment will be completely trust-worthy in such regions because their apparatus provides excellent information on the tracking and identification of scattered electrons.« less

The inherent power of inelastic scattering to probe the nuclear response function in the nuclear continuum is completely exploited only in the coincident detection of decay products. The coincidence requirement effectively eliminates the strong elastic radiative tail which hitherto plagued the analysis of single arm (e,e’) experiments. Large physical backgrounds (e.g. due to multistep processes as encountered in inelastic hadron scattering) are negligible due to the dominance of single photon exchange. Thus, coincidence electron scattering is a unique tool for quantitatively testing modern calculations of the nuclear response function. We have measured 238U(e,e’f) cross sections at three values of the momentum transfer (q≊0.26, 0.40, and 0.55 fm−1, which correspond closely to the first maxima of the E1, E2/E0, and E3 form factors respectively) from below fission threshold to 23 MeV excitation energy. The angular correlations were measured at six or seven angles in each run. The data permit a clear multipo...

The purpose of the paper is to present a summary of recent developments in high energy electron physics at Stanford. The material is divided into the following topics: nucleon form factors; deuteron form factors; (coincidence studies of elastic scattering, inelastic continuum studies); nuclear physics; (Ca40, Ca44 Investigations, study of the inelastic continuum in He3, magnetic octupole moments in light nuclei); shower studies at 900 MeV.

Elastic electron scattering studies from isotopes of calcium are briefly summarized. A study of the inelastic level structure of Ca40 and Ca48, as well as the quasi-elastic scattering from both isotopes was initiated. Preliminary results show the probable existence of excited levels or groups of levels previously unreported from electron scattering experiments. Especially interesting is the appearence of an 'edge' in the Ca40 spectrum beginning at an excitation energy of 15.7 MeV corresponding to the threshold of the state (Ca39 + n).

The magnetic form factors of the $1p$-shell nuclei ${\mathrm{Li}}^{6}$, ${\mathrm{Li}}^{7}$, ${\mathrm{Be}}^{9}$, ${\mathrm{B}}^{10}$, ${\mathrm{B}}^{11}$, ${\mathrm{N}}^{14}$, have been measured by high-energy electron scattering at an angle of 180\ifmmode^\circ\else\textdegree\fi{}. Incident electron energies up to 230 MeV (${q}^{2}\ensuremath{\simeq}5.2$ ${\mathrm{F}}^{\ensuremath{-}2}$) were used. The incident- and scattered-electron paths were separated by use of a uniform magnetic field. Back-ground due to charge scattering was subtracted by varying the scattering angle around 180\ifmmode^\circ\else\textdegree\fi{}. At the higher momentum transfers the scattering from those nuclei having spin $\ensuremath{\ge}\frac{3}{2}$, was dominated by the octupole moment distributions. Results are interpreted in terms of harmonic-oscillator and finite-square-well shell models. Parameters dependent only on the coupling of the angular momenta in the $1p$ shell may be obtained from the data. They show a general trend from $L\ensuremath{-}S$ coupling to $j\ensuremath{-}j$ coupling as the mass number increases, in agreement with calculations of magnetic dipole moments and energy-level schemes. The outstanding exception is ${\mathrm{Li}}^{7}$, whose form factor is accurately described by the extreme independent-particle model. ($L\ensuremath{-}S$ coupling is quite incompatible with the data.) The ${\mathrm{Li}}^{6}$ results may also be interpreted in terms of an "alpha plus deuteron" model. Numerical results for the harmonic-well strengths are obtained and compare favorably with electron-charge-scattering values. It is also possible to estimate magnetic octupole moments, where applicable, with fair accuracy, although these estimations are to a certain extent model-dependent.