Cross sections and density-matrix elements for π−p→ϕn have been measured for - −t≲1.5 GeV2 at 3, 4, 5, and 6 GeV/c, using the Argonne effective-mass spectrometer to observe the decay ϕ(1019)→K+K−. This is the first observation of the reaction in this energy range. The remarkably flat differential cross section at 4 GeV/c and the strong energy dependence suggest a production mechanism not normally seen at these energies. Data on K−p→ϕΛ and K−p→ϕΣ0 from the same experiment are also presented.
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Differential cross sections for π0 and ρ0 photoproduction from protons have been measured at photon energies 6, 12, and 18 GeV and momentum transfers 0.5 to 3 (GeVc)2.
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We have measured the cross section, the distribution of scattering angles, and the distribution of noncoplanarity angles for electron-positron elastic scattering at 5 GeV c. m. energy. An analysis based on 230 events with scattering angles between 50 and 130° yields a ratio of the experimental to theoretical quantum-electrodynamic cross section of 1.03 ± 0.09. The scattering-angle and noncoplanarity-angle distributions are also found to be in excellent agreement with the quantum-electrodynamic predictions.
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We have measured the reaction cross section for p¯p→n¯n in small momentum steps between 0.97 and 3.13 Gev/c to a high level of statistical accuracy. Structures are observed in the vicinity of Plab=1.25 GeVc and 1.8 GeVc which are consistent with the structure observed in the p¯p total cross section.
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Differential cross sections for the elastic scattering of K + mesons on protons have been measured at 12 lab momenta between 130 and 755 MeV/ c using a hydrogen filled bubble chamber. The results are consistent with a repulsive S-wave nuclear force. A phase-shift analysis yielded the following values of the low-energy parameters: a S 1 2 =(0.309±0.002) fm , r S 1 2 =(0.032±0.02) fm a P 1 2 =(0.021±0.002) fm , a P 3 2 =(0.013±0.001) fm 3
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We have measured the cross section σ for electron - positron annihilation into three or more hadrons, with at least two charged particles in the final state, at 5 GeV center-of-mass energy. We find a model-independent lower limit of σ>9.1±1.0nb; assuming invariant phase-space production of pions, we calculate the detection efficiency of our detector to be (45 ± 11)%, yielding a cross section σ=21±5nb. The average charged hadron multiplicity is found to be n¯=4.3±0.6.
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Differential cross sections for K−p→K¯0n and K+n→K0p have been measured at 3, 4, and 6 GeV/c using a data sample of 6000 events. Contrary to simple exchange-degenerate models, the ratio of K+ to K− cross sections was found to be approximately 1.35, with little dependence on either s or t. Both reactions show a shallow dip near the forward direction, suggesting the importance of spin-flip amplitudes.
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LARGE -T CONTRIBUTIONS (TYPICALLY 12 PCT) ESTIMATED FROM BUBBLE-CHAMBER DATA.
Total cross sections of p¯p and p¯d have been measured between 360 and 1050 MeV/c, with high statistical precision. Structures are observed in both cross sections at about the same momenta. For p¯p, the central mass is 1932±2 MeV/c2, and a fit to the data with a simple Breit-Wigner resonance plus background gives Γ=9−3+4 MeV/c2. The data suggest that the structures are in the isospin-1 state.
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The charged-particle multiplicity distribution in 205−GeVc proton-proton interactions is presented. In addition, the total diffractive contributions to each charged multiplicity are estimated assuming a factorizable Pomeron.
THE TOTAL CROSS SECTION NORMALIZATION COMES FROM THIS AND OTHER EXPERIMENTS.
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 (?////).