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The final states\(\bar p\)pω and\(\Delta ^{ ++ } \bar \Delta ^{ -- } \pi ^0 \), produced in the reaction\(\bar p\)p →\(\bar p\)pπ+π−π0 (6435 events) at 5.7 GeV/c, are studied. Cross-sections are presented, and general features of the resonances produced are investigated. Spin alignment of the ω’s, reported earlier, is studied. An enhancement is observed in the ωp (ω\(\bar p\)) mass plot of mass (1810±15) MeV and width (87 ± 20) MeV.
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X ERROR D(EKIN) = 0.0600 MEV.
The reaction e − + p → e − + p + η has been studied in the region of the S 11 (1535)-resonance by detecting the recoil proton in coincidence with the scattered electron. The reaction has been observed at three four-momentum transfers of the virtual photon: q 2 = 0.2, 0.28 and 0.4 (GeV/ c ). First results of the differential cross section measurements are given and compared with quark model calculations.
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The reaction e − + p → e − + p + π 0 has been studied in the region of the Δ (1236) resonance at a four-momentum transfer of the virtual photon of 0.3 (GeV/ c ) 2 . Angles and momenta of the secondary electron and of the outgoing proton were measured in coincidence to obtain the angular dependence of the differential cross section. The angular distribution for s- and p-waves of the pion in the πN cm-system was fitted to the cross section for three W -bins around the maximum of the resonance. The contribution of the resonant multipoles M 1+ , E 1+ and S 1+ to the cross section as well as the contribution of the background amplitudes M 1− , E 0+ and S 0+ are given.
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We give the cross-sections of quasi-two-body reactions produced in K−-proton interactions at 13 different energies in the centreof-mass energy range 1.915 to 2.168 GeV.
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The missing-mass technique has been used to study the spectra of neutral mesons produced by 2- and 3-Gev protons in the reaction p+d→He3+x0. Cross sections (dσdΩc.m.) of about 10−34 cm2/sr were observed for the π, η, and ω for 3-GeV protons. A peak with a much smaller cross section was observed at a mass of 956 MeV. We have tentatively identified this peak as the η′. Cross sections for the π and η were nearly a factor of 10 larger at 2 GeV than at 3 GeV. Deviations from simple phase space were observed near the two-pion threshold in both 2-GeV and 3-GeV data. Details of the experimental method and of the results are presented.
Axis error includes +- 0.0/0.0 contribution (?////).
The reactions of positive pions with protons yielding four charged particles and one or more neutrals have been studied, especially the reaction π+p→Δ++ω0→pπ+π+π−π0. The results presented in this paper were obtained from a 100 000-picture exposure of the Argonne-MURA 30-in. liquid hydrogen bubble chamber, with a beam of incident pions of 4.09−GeVc momentum. Comparisons have been made with corresponding results of other experiments at various incident beam momenta, and with the predictions of some theoretical models of the π+p interaction.
INCLUDING CORRECTIONS FOR BACKGROUND.
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A novel form of mass spectrometer has been used to measure the masses, widths, and cross sections of the η, ω, X0(958), and φ mesons near their respective thresholds in the reaction π−+p→missingmass+n. The incident momentum is varied in small steps through the threshold while neutrons of a given momentum are detected near zero degrees. The lower limit of the c.m. momentum P* at which measurements have been made ranges from about 50 MeV/c at the φ to about 30 MeV/c at the η. A somewhat low value for the ω mass, 782.3 ± 0.6 MeV, is found. The width of the X0 is < 1.9 MeV (95% confidence level). All four mesons show evidence of S-wave production, with values of σP* of 21.2 ± 1.8, 0.35 ± 0.03, and 0.29 ± 0.06 μb/(MeV/c) for the η, X0, and φ, respectively. A rapid rise in the ω cross section appears to be modified by a final-state interaction. The effect of this rise can probably be seen in some S11 pion-nucleon phase-shift solutions. Evidence is also presented of a sudden drop in the π+π− mass spectrum just above the threshold for the production of a K+K− pair. The paper includes a comprehensive discussion of the method and of the details of the spectrometer.
CROSS SECTIONS NEAR THRESHOLD.
Cross sections for inelastic scattering of electrons from hydrogen and deuterium were measured for incident energies from 4.5 to 18 GeV, at scattering angles of 18°, 26°, and 34°, and covering a range of squared four-momentum transfers up to 20 (GeVc)2. Neutron cross sections were extracted from the deuterium data using an impulse approximation. Comparisons with the proton measurements show significant differences between the neutron and proton cross sections.
Axis error includes +- 1/1 contribution (DUE TO ERRORS IN ABOVE CORRECTIONSFOR DEAD-TIME LOSSES, INEFFICIENCIES IN E- IDENTIFICATION).
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