Search

The properties of a large NaI(Tl) detector as a total absorption detector for pions at GeV energies are reported. These observations are supplemented by measurements on the three-dimensional distribution of deposited energy in a large absorber of metallic tin by GeV pions. The latter data are compared with existing Monte Carlo calculations of the nucleon-meson cascade and their application to the design of total absorption detectors with large containment factors is discussed.

The electron scattering at high momentum transfer has been measured from the nucleons in Be, in C, and from the free proton. The data yield the cross section of the average nucleon and of the neutron in relation to that of the proton. $\frac{{\ensuremath{\sigma}}_{n}}{{\ensuremath{\sigma}}_{p}(\ensuremath{\theta})}$ is found to be 1.16\ifmmode\pm\else\textpm\fi{}0.3 at 500 Mev and 135\ifmmode^\circ\else\textdegree\fi{}; it decreases, as expected, for smaller angles and lower energies. If the assumption is made that meson-exchange effects and interactions in the final state are not important, the form factors obtained indicate an apparent root-mean-square radius of the neutron's magnetic-moment distribution of (0.53\ifmmode\pm\else\textpm\fi{}0.15)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm. It is possible that the apparent small size of the neutron in Be and C is due to the neglect of meson-exchange effects and interactions in the final state. The present result is smaller than a neutron size, given by Yearian and Hofstadter, who compared the cross sections of deuteron and proton and found equal sizes for neutron and proton. If one accepts the latter result, the present experiment can be used to yield a measure of the above neglected effects.

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.)

A scintillation counter telescope, employing three NaI(Tl) crystals in coincidence, has been used to study the energy losses experienced by mu-mesons in traversing one of the crystals. The magnitude of the light flash in NaI(Tl) has been assumed to be proportional to the energy lost in the crystal by the meson. The observed pulse distribution is compared with one calculated on the basis of the Bethe-Bloch theory without the density correction and also with the Halpern-Hall theory which includes the effect of the dielectric shielding. Each calculated curve employs a fold of the Landau straggling theory with the cosmic-ray mumeson spectrum. Comparison of the data with the two theories definitely favors the Halpern-Hall theory both in respect to absolute value of the most probable energy loss as well as the shape of the distribution.

A new method is described for determining gamma-ray energies and intensities. The basis of the method is the observation of narrow pulse distributions (lines) in the scintillations of NaI(T1). Due to the presence of the iodine component, pair production and the photoelectric process produce relatively sharp lines in the pulse distributions. The Compton process may also be used in determining gamma-energies. Approximate theoretical curves of the pulse distribution are shown. Experimental spectra resemble the theoretical patterns, except for differences in intensities discussed in the text. Electronic as well as photographic techniques for obtaining spectra are described. With these methods well known spectra are confirmed and new results in the case of ${\mathrm{Ga}}^{66}$ are given. With a source of less than ${10}^{\ensuremath{-}9}$ curie of ${\mathrm{K}}^{40}$ the energy of the gamma-ray has been determined to within two percent. The method described should make possible a new approach to the study of weak gamma-radioactivities and unknown gamma-ray spectra.

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 infra‐red absorption spectra between 1 and 15.5μ of the monomer and dimer of HCOOD have been found with a rocksalt prism spectrometer. The position of the vibration characteristic of the ``deuterium bond'' in HCOOD has been determined and permits an approximate calculation of the shorter OD distance in the dimer ring. As in CH3COOD the distance is found to be 1.07A.

The structure and size of the proton have been studied by means of high-energy electron scattering. The elastic scattering of electrons from protons in polyethylene has been investigated at the following energies in the laboratory system: 200, 300, 400, 500, and 550 Mev. The range of laboratory angles examined has been 30\ifmmode^\circ\else\textdegree\fi{} to 135\ifmmode^\circ\else\textdegree\fi{}. At the largest angles and the highest energy, the cross section for scattering shows a deviation below that expected from a point proton by a factor of about nine. The magnitude and variation with angle of the deviations determine a structure factor for the proton, and thereby determine the size and shape of the charge and magnetic-moment distributions within the proton. An interpretation, consistent at all energies and angles and agreeing with earlier results from this laboratory, fixes the rms radius at (0.77\ifmmode\pm\else\textpm\fi{}0.10) \ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm for each of the charge and moment distributions. The shape of the density function is not far from a Gaussian with rms radius 0.70\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm or an exponential with rms radius 0.80\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm. An equivalent interpretation of the experiments would ascribe the apparent size to a breakdown of the Coulomb law and the conventional theory of electromagnetism.

In the present study the absorption spectrum of formic acid vapor between 1 and 15.5μ has been investigated under a variety of temperature conditions. The spectrum at room temperature gives essentially the absorption of the double molecules alone, while that at 140°C gives the absorption of the single molecules. The results are interpreted in terms of the hydrogen bonding existing in the double molecule. In addition an attempt to prepare and investigate pure formic acid‐d is reported.

The electromagnetic form factors of the neutron have been measured in the ${q}^{2}$ range from 1.0 to 30.0 ${\mathrm{F}}^{\ensuremath{-}2}$. It is found that for values of ${q}^{2}$ greater than about 6.0 ${\mathrm{F}}^{\ensuremath{-}2}$ the square of the neutron's charge form factor ${({G}_{\mathrm{En}})}^{2}$ is consistent with zero to within an error of the order of 5% in the existing theoretical cross section. For values of ${q}^{2}$ less than 6.0 ${\mathrm{F}}^{\ensuremath{-}2}$ it is concluded that meaningful values of the neutron form factors cannot be given until the necessary corrections to the theory are better understood. The present results on the neutron form factors are combined with recent measurements of the proton form factors to provide experimental determinations of the isotopic nucleon form factors. It is found that the $\ensuremath{\omega}$ and $\ensuremath{\phi}$ mesons provide a good approximation to the observed isoscalar form factors but that it is difficult to understand the behavior of the isovector form factors in terms of the $\ensuremath{\rho}$ meson alone.

An experimental determination has been made of the radial and longitudinal distribution of energy produced in showers initiated by electrons of 118 Mev and 157 Mev in copper. A small crystal CsBr(Tl) coupled to a thin light pipe and photomultiplier was used as a probe. Graphs of the radial distributions are given from which, by numerical integration, transition curves are determined. Calculations are made for an approximately optimum design of scintillation crystal [e.g., NaI(Tl)] to capture a large fraction of the energy within a shower.

The ${\mathrm{Li}}^{6}$ nucleus has been studied at 426 Mev by electron scattering methods between laboratory angles of 33\ifmmode^\circ\else\textdegree\fi{} and 57.5\ifmmode^\circ\else\textdegree\fi{}. Absolute values of the ${\mathrm{Li}}^{6}$ cross sections have been obtained by comparison with scattering measurements made on the proton at 426 Mev and 40\ifmmode^\circ\else\textdegree\fi{}. Unique values of the experimental form factors are given in tabular form. The results are analyzed in terms of various possible charge distributions. Several examples of models showing a good fit are presented and appropriate radius and skin thickness values are given. Several unsuccessful models are also discussed.

Absolute values of the most probable energy loss and the energy-loss straggling for high-energy muons passing through NaI (T1) have been measured over the muon momentum range from 0.5 to 10.5 $\frac{\mathrm{GeV}}{c}$. The results agree, within the 1% experimental uncertainty, with the theoretical values.

Elastic scattering of 192-Mev electrons from deuterium has been studied using both solid (C${\mathrm{D}}_{2}$) and high-pressure gas targets. The results obtained by these two methods are in agreement and yield the following conclusions: (1) The range of the neutron-proton potential is between 1 and 4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm if a square potential well is assumed and if the deuteron wave functions predicted by the binding energy of the deuteron are used. (2) It is, however, impossible with the present data to eliminate the possibility of other charge distributions for deuterium such as uniform or Gaussian.Inelastic electron scattering from deuterium was also investigated, and promises to give independent information of the deuteron structure.

Separate proton form factors were obtained from electron scattering studies by choosing a pair of experimentally measured cross sections at the same value for the square of the momentum transfer but at different values of electron energy and scattering angle. The proton form factors obtained were plotted against the square of the momentum transfer. The new F/sub 2/ indicated that the Pauli magnetic moment cloud is a spread-out distribution. The constancy of F, however, suggested that the Dirac electric/magnetic cloud has a small, perhaps point-like, core. (M.C.G.)

A total absorption Nal(TI) detector can be used to define the energy of an incident electron, or γ-ray, to a precision of I to 2 per cent in the range of 4 to 14 GeV.

Mechanical, or sound, vibrations were observed in ceramic piezoelectric disks of lead-zirconate-titanate (PZT) struck by high energy electrons. Four 1/2 inch thick disks of PZT were used. A wide band, low impedence, common base configuration amplifier was used to examine the induced vibrations. Since the most prominent resonant frequencies of the disks were near 40 kHz (radial mode) and 158 kHz (compressional mode) most of the studies were concentrated on these modes. Electrons of energy 1.00 BeV and 0.20 BeV were used in pulses, each lasting about 1.0 microsecond and contained 10,000 to 1,000,000 to electrons. The cross section of the incident 1.00 BeV beam was about 3 mm x 3 mm. (Author)

A large double-focusing magnetic spectrometer, capable of analyzing electrons or other singly-charged particles up to a momentum of 1000 Mev/c, was used in studies of electron scattering from protons at incident electron energies of 650 to 900 Mev between scattering angles of 45 and 145 deg . Typical electron peaks are shown. Values are given for scattering angle, cross section, and square of the momentum transfer. (M.C.G.)

A conventional potentiometer, wound uniformly on a cylindrical card of constant height, can be used to provide a close approximation to the tangent of an angle in terms of a voltage or current. Curves showing the degree of approximation are presented in the range (0, ±80°). By using a slight taper in the height of the card the tangent can be provided exactly, except for winding errors.

Scintillation crystals of CaI2 and CaI2(Eu) have been produced which iypically show pulse heights of 180% relative to NaI(Tl). The emission spectra for both pure and activated materials are well matched to a S-ll phototube response. Pure CaI2 has a decay time of 0.55, ?sec; CaI2(Eu) has a 0.79, ?sec decay time. Though this material is difficult to grow and to package, performance results thus far obtained are encouraging.

The subject of laser induced fusion has advanced by some dramatic steps in the last few years. The following article by the staff of KMS Fusion outlines some of these events. I have had the pleasure of being associated with the group while many of the experiments were being carried out. I feel that the high values of volumetric compression achieved speak for the eventual success of this method of generating large numbers of neutrons. The neutron yield has increased from a few thousand to 7 × 106 in a comparatively short time and the various tests that have been conducted lead me to believe that the neutrons are of thermonuclear origin.

We have searched for radiative decays of the ϒ(1S) resonance, ϒ(1S)→γX, whereX is one of the mesons η, η′f2 (1270),f2 (1720), or a narrow resonance with mass less than 3 GeV/c2 which decays into either π0π0 or ηη. The mesons are identified in their all-neutral decay modes. Since we do not find any such decays, we calculate upper limits on the corresponding branching ratios. These limits are compared to theoretical predictions and to the corresponding branching ratios measured in radiativeJ/Ψ decays.

This paper discusses the early history of the electron scattering program and illustrates results concerning nucleons and nuclei.

With apparatus previously described1,2 we have studied the elastic scattering of electrons of energies 100, 188, and 236 MeV from protons initially at rest. At 100 MeV and 188 MeV, the angular distributions of scattered electrons have been examined in the ranges 60°-138° and 35°-138°, respectively, in the laboratory frame. At 236 MeV, because of an inability of the analyzing magnet to bend electrons of energies larger than 192 MeV, we have studied the angular distribution between 90° and 138° in the laboratory frame. In all cases a gaseous hydrogen target was used.

The aim was the development of an angiographic method and appropriate equipment for imaging with x-rays the coronary arteries in a non-invasive manner. Successive steps involved studies with phantoms, live animals and finally with human subjects. Clinical evaluation of human coronary arteries remains a goal of this and a continuing project, and steps along the way to such an achievement are in process. Transvenous injection of a dye using the method of iodine dichromography near 33.2 keV, the K-edge of iodine, forms the basis of the method. 11 refs.

In concluding this discussion it may be appropriate to return to the theme introduced earlier and raise the question once again of the deeper, and possibly philosophical, meaning of the term "elementary" particle. As we have seen, the proton and neutron, which were once thought to be elementary particles, are now seen to be highly complex bodies. It is almost certain that physicists will subsequently investigate the constituent parts of the proton and neutron—the mesons of one sort or another. What will happen from that point on? One can only guess at future problems and future progress, but my personal conviction is that the search for ever-smaller and ever-more-fundamental particles will go on as long as man retains the curiosity he has always demonstrated ( 29 ).

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.

The electron-and bremsstrahlung-induced fission cross sections of the isotopes $_{92}^{238}\mathrm{U}$, $_{83}^{209}\mathrm{Bi}$, $_{82}^{208}\mathrm{Pb}$, $_{70}^{174}\mathrm{Yb}$, and $_{62}^{154}\mathrm{Sm}$ have been measured over the energy range 60-1000 MeV. The consistency of the theoretical expressions for the bremsstrahlung spectrum and the virtual-photon spectrum associated with the electron has been tested using the experimental data. Good agreement was obtained on the assumption of $E1$ or $M1$ transitions. The photofission cross sections obtained on the basis of this procedure were analyzed in terms of the photon-interaction cross section and the fission probability. It was found that the rapid increase in the photofission cross section with increasing energy for $^{209}\mathrm{Bi}$ and the lighter isotopes is due to the normal increase in fission probability with energy, and not to the onset of $\ensuremath{\pi}$-meson photoproduction as was previously suggested. The photon-interaction cross section predicted by the quasideuteron model seems to account for all of the interaction leading to fission in these elements, even at energies above the threshold for $\ensuremath{\pi}$-meson production. In the case of $^{238}\mathrm{U}$, however, since the fission probability is approximately constant as a function of energy, the fission cross-section behavior reflects the characteristics of the total photon-interaction cross section. In the latter case it was found that the $\ensuremath{\pi}$-meson photoproduction and the quasideuteron interaction are both involved in producing excitation leading to fission. The difference between the behavior of $^{238}\mathrm{U}$ and the lighter isotopes is understood in terms of differences in fission barriers and differences in energy deposition associated with the two interaction mechanisms. The asymmetric fission of $^{238}\mathrm{U}$ at high electron or bremsstrahlung energies is also explained on this basis.

The original elastic electron scattering experiments on nuclei produced charge distributions that were characterized by two basic parameters; the half-density radius r0.5 and the skin thickness t . It was possible using a phenomenological charge distribution, containing only these two parameters, to fit the experimental data from a wide range of nuclei. This situation has changed considerably in recent years. The amount of experimental cross sections in existence has increased and the data has been extended to higher values of the recoil momentum q . The ability to measure cross sections at larger values of q together with the better accuracy of the experimental data allows details of the charge distribution to be seen that were previously unobservable.

My purpose in this paper is to suggest that it is possible to bring precision to the processes of detection of particles and photons of very high energies. I have felt for a long time that high energy physics will someday turn into a spectroscopic subject and at that time high resolution methods will be essential to further developments. In the past few years I have been trying to advance the detection technique in two ways. One involves the straightforward development of a precise, large-solid-angle magnetic spectrometer capable of resolving momenta to one part in ten thousand. The second technique is concerned with the total absorption method of detection, and this is the actual subject of the present paper.

The Crystal Ball detector at thee+e− storage ring DORIS-II has been used to search for radiativeB meson decays, especially of the typeb→sγ. No monoenergetic γ-lines have been found in the inclusive photon spectrum from У(4S) decays, and upper limits are obtained for radiative decays ofB mesons to various strange mesons and to theD*. Integrating the photon spectrum over the corresponding energy range, we find $$BR(B \to \gamma X)< 2.8 \times 10^{ - 3} ,$$ at 90% confidence level for the mass range 892 MeV ≦MX≦2045 MeV.

The Crystal Ball Collaboration has measured the energy spectrum of electrons from semileptonicB meson decays at thee + e − storage ring DORIS II. Branching ratios and weak mixing angles of the Kobayashi-Maskawa matrix are determined using several models for the hadronic matrix elements. We obtain the branching ratio for semileptonic.B decays to charmed states BR(B→evX c )=(11.7±0.4±1.0)%. Our result for the corresponding Kobayashi-Maskawa matrix element is |V cb |=0.052±0.006. The model dependence of both results is included in the error. We have not observed semileptonicB decays to non-charmed mesons. Analyzing the measured electron spectrum above 2.4 GeV, where nob→c decays contribute, we find BR(B→evX u )/BR(B→evX c )

We give the experimental elastic cross sections for $^{40}\mathrm{Ca}$ at 757.5 MeV.NUCLEAR STRUCTURE Electron scattering.