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Axis error includes +- 0.0/0.0 contribution (?////).
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A 14-in. liquid-hydrogen-filled bubble chamber in a 17.5-kG magnetic field was exposed to a beam of negative pions produced by the Cosmotron at Brookhaven National Laboratory. About 26 000 pictures were taken and examined for the following final states: (1) elastic scattering (π−p); (2) π+ production (π−π+n); (3) π0 production (π−π0p); (4) neutrals. Values for the cross sections for these processes are σ(elastic)=17.56±0.43 mb, σ(π+)=7.14±0.23 mb, σ(π0)=4.65±0.17 mb. The elastic-scattering angular dependence in the c.m. system is fitted by a power-series expansion in cosθ and gives the following coefficients: a0=0.27±0.02, a1=1.48±0.11, a2=3.86±0.22, a3=−0.29±0.53, a4=−0.65±0.28, a5=1.69±0.52 (units: mb/sr). Cross sections for multiple-pion production were also measured: σ(π−π+π0n)=0.33±0.04 mb, σ(π−π+π−p)=0.08±0.02 mb. The total neutral cross section was σ(neutrals)=11.78±0.43 mb; the total charged events cross section was σ(charged)=29.76±0.69 mb; and the total cross section was σ(total)=41.54±0.82 mb. For single-pion production events, two-body mass distributions and angular distributions were compared with the predictions of the Olsson-Yodh isobar model.
Axis error includes +- 0.0/0.0 contribution (?////STATISTICAL YIELD DOMINATES).
We present results on elastic electron-deuteron experiments performed at Orsay. The range of momentum transfers is 0.6 to 2 F−2. Two kinds of measurements have been taken detecting the scattered electron: one with a solid CD2 target, the other with a liquid target. The data are analyzed with the nonrelativistic theory, which gives slightly positive neutron form factors and a magnetic neutron form factor nearly equal to the magnetic proton form factor.
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Angular distributions of recoil-proton polarization in elastic π±p scattering were measured at 864-, 981-, and 1301-MeV incident pion kinetic energy. Polarization measurements were made by observing the azimuthal asymmetry in the subsequent scattering of recoil protons in large carbon-plate spark chambers. The spark chambers proved to be very suitable polarization analyzer detectors. Strong variation of the polarization with backward pion scattering angle was observed.
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Angular distributions of recoil-proton polarization in elastic π±p scattering were measured at 523-, 572-, and 689-MeV incident pion kinetic energy. Polarization measurements were made by observing the azimuthal asymmetry in the subsequent scattering of recoil protons in large carbon-plate spark chambers. Typical strong variation of the polarization with pion scattering angle near the πp diffraction minima was observed. Since existing opinion favors a D13 resonance at 600 MeV, a phase-shift analysis was attempted in order to confirm the existence and parity of this resonance. Available πp total and differential cross sections, these polarization data, and some possible restrictive assumptions related to the 600-MeV resonance were used in the analysis. Though the polarization results aided significantly in restricting the number of acceptable phase-shift sets, still, many plausible and qualitatively different sets were found.
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The differential cross section for the photoproduction of a π− meson from the neutron bound in the deuteron was measured for pion laboratory angles of 76°, 96°, and 118° at incident gamma-ray energies in the region of 275 MeV. The π− meson and the high-energy proton were detected. The pion momentum and angle were measured by sets of spark chambers situated in front of and behind a magnetic field. The proton angle and range were also measured with spark chambers. To calculate "free" neutron cross sections from our data, we used a modified version of the extrapolation method suggested by Chew and Low. By observing the π+ only, the differential cross section for π+ photoproduction from hydrogen also was measured. As determined by this experiment, the differential cross section for photoproduction of a π− meson from a "free" neutron and the differential cross section for photoproduction of a π+ meson from hydrogen are as follows: Eγlab≃275 MeV These results disagree with the dispersion theory predictions of Chew, Goldberger, Low, and Nambu. They also disagree with McKinley's dispersion theory calculations which include a bipion or ρ-meson term in the production amplitudes.
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