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An experiment designed to study the π−p total neutral cross section and its breakdown into several channels has been performed at eleven incident pion momenta ranging from 654 to 1247 MeV/c. Angular distributions for the charge exchange π0 and for η0 production are given in terms of Legendre-polynomial expansion coefficients. Forward and backward differential cross sections are presented for the charge-exchange channel and comparisons with recent dispersion-relation predictions for the forward cross section are made.
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The reaction γ⊥,∥p→π+n has been studied with linearly polarized photons of energy 3.0 GeV at −t values between 0.15 and 1.2 (GeVc)2. The asymmetry A+=(dσ⊥−dσ∥)(dσ⊥+dσ∥) is found to be positive throughout this four-momentum-transfer range, implying the dominance of natural parity exchange in the t channel. Comparison of dσ⊥(γ⊥p→π+n) and dσ⊥p→π−p) from a previous experiment indicates strong interference between the isoscalar and isovector photon amplitudes for photons polarized perpendicular to the production plane.
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The angular distribution of proton-proton elastic scattering has been measured for incident beam momenta of 10.0, 12.0, 14.2 and 24.0 GeV/ c over a range of laboratory scattering angles from 12 to about 140 mrad. The results are compared with the fourth power of the electromagnetic form of the proton.
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At 3 GeV/ c , the total and differential cross sections of the reactions K − n → Y π − have been determined for nine S = −1 baryonic states. Backward peaks associated with a dip near u = −0.2 are observed in many cases. They have been interpreted, for the isospin-zero Y-states, in terms of a proton-exchange mechanism. The backward peaks in the reactions K − n → Λπ − and K − n → Σ o π − have been more quantitatively related to the backward π N → N π differential cross sections at the same energy. This comparison leads to the conclusion, that the first reaction is dominated by nucleon exchange, whereas the second one requires a more complex exchange mechanism.
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We have measured the reaction γ+n→π0+n at a photon energy of 4 GeV for 0.2<~−t<~1.8(GeVc)2. The cross section is slightly less than that with protons as a target.
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Nucleon resonance production in the two-body reaction p + p → p + N ∗ has been studied at 24 GeV/ c incident momentum for angles from 12 to 117 mrad by measuring proton momentum spectra from the elastic peak down to a momentum corresponding to a missing mass of about 2.6 GeV.
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Proton-proton elastic scattering has been measured over the angular range 7 to 16 mrad at centre-of-mass energies of 31, 45 and 53 GeV using the CERN Intersecting Storage Rings. The results indicate that the diffraction peak has continued to shrink with increasing energy, but not as fast as suggested by the results at lower energies.
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3 H̃e nuclei were observed in the negative beam, produced by 70 GeV protons on an Al target. Five 3 H̃e have been identified among 2.4 · 10 11 particles that passed through the apparatus. Scintillation and Čerenkov counters were used to measure the electrical charge and velocity of particles. The mass of 3 H̃e is found to be M 3 H ̃ e = (1.00 ± 0.03)3m p , the charge is z = (0.99 ± 0.03)2 e . The ratio of differential production cross sections of 3 H ̃ e (P = 20 GeV /c) and π − (P = 10 GeV/c ) equals 2 · 10 −11 . This corresponds to antihelium −3 production cross section d 2 σ 3 H ̃ e / d Ω d P = 2.0 · 10 −35 cm 2 / sr · GeV /c per Al nuclei and 2.2 · 10 −36 cm 2 sr · GeV/ c per nucleon.
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We have studied the reaction e−+p→e−+π++n by detecting the final electron and pion in coincidence. Data are presented in the region of virtual photon mass squared from -0.18 to -1.2 GeV2, and virtual photoproduction center-of-mass energy and angle from 1.85 to 2.50 GeV and 0 to 20°, respectively.
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