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Antiproton-production and nucleon-interaction cross sections were investigated for antiprotons in the energy range 0.5 to 1.0 BeV. The antiprotons were distinguished from other particles produced at the Bevatron by a system of scintillation and velocity-selecting-\ifmmode \check{C}\else \v{C}\fi{}erenkov counters. The excitation function and momentum distribution were recorded for antiproton production in carbon and compared with statistical model expectations.The antiprotons were directed by a system of bending and focusing magnets to a liquid hydrogen target. An array of plastic scintillation counters, which almost completely surrounded the hydrogen target, was used to determine the $\overline{p}\ensuremath{-}p$ total, elastic, inelastic, and charge-exchange cross sections. Near 500 MeV the total $\overline{p}\ensuremath{-}p$ cross section is about 120 mb, and it slowly decreases to 100 mb near 1 BeV. The inelastic cross section, which is principally due to the annihilation process, represents nearly $\frac{2}{3}$ of the total cross section. The elastic-scattering distribution is highly peaked in the forward direction and can be fitted by an optical model.The total and partial cross sections were also determined for the collisions of antiprotons with deuterons. The $\overline{p}\ensuremath{-}d$ total and inelastic cross sections were found to be approximately 1.8 times the $\overline{p}\ensuremath{-}p$ cross sections. Corrections were made for the shielding of nucleons within the deuteron in order to ascertain the $\overline{p}\ensuremath{-}n$ interaction. The results indicate that the $\overline{p}\ensuremath{-}p$ and $\overline{p}\ensuremath{-}n$ cross sections are very nearly equal in this energy region, and that they satisfy the inequalities required by charge independence.

The polarimeters needed to monitor and measure electron beam polarization at the Stanford Linear Collider are discussed. Two types of polarimeters, are to be used. The first is based on the spin dependent elastic scattering of photons from high energy electrons. The second utilizes the spin dependence of elastic electron-electron scattering. The plans of the SLC polarization group to measure and monitor electron beam polarization are discussed. A brief discussion of the physics and the demands it imposes on beam polarization measurements is presented. The Compton polarimeter and the essential characteristics of two Moeller polarimeters are presented. (LEW)

The recoil-proton polarization in {pi}{sup +}-p elastic scattering at 310-Mev incident-pion laboratory kinetic energy has been experimentally measured at four scattering angles with scintillation counters. Polarization values obtained, related rms experimental errors, and mean center-of-mass recoil angles are: +0.044 {+-} 0.062 at 114.2 deg. =0.164 {+-} 0.057 at 124.5 deg, -0.155 {+-} 0.044 at 133.8 deg, and -0.162 {+-} 0.037 at 145.2 deg. The sign of the polarization is defined to be positive when a preponderance of the recoil protons had their spin vectors pointing in the direction of {rvec P}{sub i} x {rvec p}{sub f}, where this quantity is the cross product of the initial and final momentum vectors of the conjugate pions. A beam of 1 x 10{sup 6} pions per sec incident upon a 1.0-g/cm{sup 2}-thick liquid-hydrogen target produced the recoil protons, which were then scattered by a carbon target at a mean energy varying with recoil angle from 113 to 141 Mev. The polarization of the recoil protons was analyzed by measuring the asymmetry produced in the carbon scattering. A proton beam of known polarization was used to determine the analyzing ability (measured asymmetry divided by the polarization of the incident protons) of the system atmore » each recoil angle. Values obtained for the analyzing ability range from 0.41 to 0.57.« less

A comprehensive phase-shift analysis of ${\ensuremath{\pi}}^{+}\ensuremath{-}p$ elastic-scattering data at 310-Mev incident-pion laboratory kinetic energy has been performed. The experimental data utilized include measurements of the differential and total cross sections and of the recoil-proton polarization. The $D$-wave phase shifts were found to be definitely needed in order to attain an adequate fit to the data. A general search for phase-shift solutions was carried out, using $S$-, $P$-, and $D$-wave phase shifts. One solution\char22{}of the Fermi type\char22{}was found that fits the data significantly better than any of the other solutions obtained. The calculated errors in the phase shifts of this set vary from 0.4 to 0.6 deg. Because it was felt that these errors might be deceivingly restrictive, the effects of small nuclear $F$-wave phase shifts on the results of the analysis were investigated and were found to be large: not only are the uncertainties in the original Fermi-type solution increased, but additional sets of phase shifts arise that fit the data well. One of these new solutions is similar to the original Fermi set except that the magnitudes of the phase shifts in this new fit are in general larger than those in the initial solution, and the signs of the $D$-wave phase shifts are reversed. The nuclear phase shifts in the original Fermi solution and their rms errors are (when $F$-wave phase shifts are allowed): ${S}_{3,1}=\ensuremath{-}17.2\ifmmode\pm\else\textpm\fi{}2.6$ deg, ${P}_{3,1}=\ensuremath{-}2.9\ifmmode\pm\else\textpm\fi{}4.0$ deg, ${P}_{3,3}=135.0\ifmmode\pm\else\textpm\fi{}0.6$ deg, ${D}_{3,3}=3.1\ifmmode\pm\else\textpm\fi{}2.6$ deg, ${D}_{3,5}=\ensuremath{-}4.9\ifmmode\pm\else\textpm\fi{}2.1$ deg, ${F}_{3,5}=0.5\ifmmode\pm\else\textpm\fi{}0.6$ deg, ${F}_{3,7}=\ensuremath{-}0.6\ifmmode\pm\else\textpm\fi{}1.4$ deg. Although theory appears to favor this set, further theoretical and experimental evidence is desirable. The values given here for the first five phase shifts approximate the corresponding values obtained when the $F$-wave phase shifts were assumed negligible. However, all except ${P}_{3,3}$ fall outside the limits set by the small original errors. Inelastic-scattering processes were neglected during the phase-shift analysis. Calculations indicate that, if these processes could properly be taken into account, any changes in the quoted values of the phase shifts would probably be well within the corresponding errors given here. Extension of the phase-shift inquiries to include $G$ waves was attempted, but it was observed that the available data and theory do not allow the $G$-wave interaction to be significantly incorporated into the analysis.

The measurements yielded information on the antiproton-carbon scattering cross section for scattering; angles of 5 deg (lab) or more. A total of 70 antiprotoncarbon scattering events were seen in a total antiproton path length of 179 meters of liquid propane (density = 0.42 g/cm/sup 3/). The high ratio of the total antiproton cross section observed at higher energies on several elements also extends to the lower energies considered. (M.H.R.)

The polarization parameter in elastic {pi}{sup -}p scattering has been measured, at the Berkeley 184 synchrocyclotron,l with the use of a polarized proton target. At 318, 337 and 390 Mev incident pion kinetic energy, the angular range from 70{sup o} to 180{sup o} in the center of mass system was covered. At 229 Mev polarization measurements were made in the angular range 150{sup o} to 180{sup o}. Phase shift analyses using these and other published data were made at the two lowest energies.

A comprehensive phase-shift analysis of {pi}{sup +}-p elastic-scattering data at 310-Mev incident-pion laboratory kinetic energy has been performed. The experimental data utilized include measurements of the differential and total cross sections and of the recoil-proton polarization. The D-wave phase shifts were found to be definitely needed in order to attain an adequate fit to the data. A general search for phase-shift solutions was carried out, using S-, P-, and D-wave phase shifts. One solution--of the Fermi type--was found that fits the data significantly better than any of the other solutions obtained. The calculated errors in the phase shifts of this set vary from 0.4 to 0.6 deg. Because it was felt that these errors might be deceivingly restrictive, the effects of small nuclear F-wave phase shifts on the results of the analysis were investigated and were found to be large; not only are the uncertainties in the original Fermi-type solution increased, but additional sets of phase shifts arise that fit the data well. One of these new solutions is similar to the original Fermi set except that the magnitudes of the phase shifts in this new fit are in general larger than those in the initial solution, and the signsmore » of the D-wave phase shifts are reversed. The nuclear phase shifts in the original Fermi solution and their rms errors are (when F-wave phase shifts are allowed): S{sub 3,1} = -17.2 {+-} 2.6 deg, P{sub 3,1} = -2.9 {+-} 4.0 deg, P{sub 3,3} = 135.0 {+-} 0.6 deg, D{sub 3,3} = 3.1 {+-} 2.6 deg, D{sub 3,5} = -4.9 {+-} 2.1 deg, F{sub 3,5} = 0.5 {+-} 0.6 deg, F{sub 3,7} = -0.6 {+-} 1.4 deg. Although theory appears to favor this set, further theoretical and experimental evidence is desirable. The values given here for the first five phase shifts approximate the corresponding values obtained when the F-wave phase shifts were assumed negligible. However, all except P{sub 3,3} fall outside the limits set by the small original errors. Inelastic-scattering processes were neglected during the phase-shift analysis. Calculations indicate that, if these processes could properly be taken into account, any changes in the quoted values of the phase shifts would probably be well within the corresponding errors given here. Extension of the phase-shift inquiries to include G waves was attempted, but it was observed that the available data and theory do not allow the G-wave interaction to be significantly incorporated into the analysis.« less

Observation of antiprotons in a propane or hydrogen bubble chamber offers the possiblity of studying several phenomena for which counter or photographic emulsion techniques are less suitable. Because there is a high ratio of pions, muons, and electrons to antiprotons in the available momentum-analyzed beams, these beams cannot be used in the bubble chamber without an initial purification, which increases the ratio of antiprotons to other particles. Such a purification has been achieved by utilizing the difference in rates of momentum loss in absorbers between antiprotons and other particles. The principle of the method is to pass a momentum-analyzed beam through an absorber. Since particles of unequal mass do not have the same specific ionization they lose different amounts of momentum, and a further magnetic deflection suffices to separate the particles physically according to mass. In this experiment a desirable momentum for antiprotons entering the bubble chamber was 684 Mev/c; however, at this momentum the ratio of undesirable particles to antiprotons at the target where they are produced is about 6 x 10{sup 5}. By starting with 970-Mev/c particles at the target and using the method of differential absorption, they decreased the ratio of undesirable particles (87% {mu}{sup -}, 105more » {pi}{sup -}, 3% e{sup -}) to antiprotons entering the bubble chamber at 684 Mev/c to 1.5 x 10{sup 4}. A system of counters indicatd when an antiproton entered the bubble chamber, and although the chamber was expanded on every Bevatron pulse, the lights were flashed and the chamber photographed only when an antiproton entered.« less

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