Results are presented from experiment WA7 at the CERN SPS, which has measured the elastic differential cross sections of π ± p, K ± p, p p and pp at incident momen ta of 20, 30 and 50 GeV/ c . The measurements cover the momentum transfer range 0.5 < | t | < 8 (GeV/ c ) 2 , corresponding to c.m. scattering angles between 10° and 50°. The experimental set-up, trigger logic and data analysis are described. The experimental results are compared with existing meson-proton and nucleon-proton data at lower and higher energies covering the medium- and large-| t | region. Some prominent models and their predictions for elastic scattering at WA7 energies and beyond are reviewed, with emphasis on geometrical scaling, factorizing eikonal models, lowest-order QCD and other dynamical exchange-type models. Results for p p two-body annihilation into π − π + and K − K + at 30 and 50 GeV/ c , obtained in parallel with the elastic p p data, are also presented.
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The reaction p p → π − π + has been studied at 10.1 GeV/ c in the − t interval from 0.15 to 1.5 (GeV/ c ) 2 . A line-reversal comparison with backward elastic scattering π + p → p π + shows good agreement for − t > 0.3 (GeV/ c ) 2 .
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A bubble-chamber experiment based on 304 000 events of p¯p interactions at 2.32 GeV/c is described. The film was automatically scanned and measured by the POLLY II system. Details of the data-analysis methods are given. We report results on cross sections for constrained final states, tests of C invariance, and inclusive pion and ρ0 multiplicity parameters for annihilation final states.
Axis error includes +- 4/4 contribution.
Axis error includes +- 4/4 contribution.
The angular distributions for the two annihilation channels p ̄ p →π + π − and p ̄ p → K + K − have been measured at 6.2 GeV/ c . The two-pion channel shows peripheral peaks for π + and π − going forward, and the two-kaon channel shows a peripheral peak for the K − going forward. The results have been compared with the line-reversed elastic backward scattering reactions and also with a constituent interchange model.
S = 13.546 GEV**2, T+U = -11.746 GEV**2, KINEMATIC LIMITS: -T = 0.063 AND 11.683 GEV**2.
S = 13.546 GEV**2, KINEMATIC LIMITS: -T = 0.036 AND 11.262 GEV**2.
The ratio (p¯d→π−π0ps)(p¯d→π−π+n) at rest, with spectator momenta ≲300 MeVc, has been measured and found to be 0.68 ± 0.07. This implies that (75 ± 8)% of the annihilations in deuterium into two pions come from odd N¯N orbital angular momenta, in disagreement with the S-state-dominance hypothesis. It has also been observed that the p¯d→π−π0ps production rate depends on the spectator momentum, which suggests energy-sensitive N¯N phenomena near threshold.
RELATIVE ANNIHILATION FREQUENCY AT REST.
Complete angular distributions for the reactions p p → π − π + and other two meson states at 2.3 GeV/ c are presented. The extraordinary π − π + angular distribution is contrasted with the other final states and the predictions of simple models. A favourable comparison is made with the qualitative features of a dual model involving high mass meson states with a strong degeneracy with respect to I -spin.
SOME ANGULAR DISTRIBUTIONS ALSO PRESENTED.
K* NEUTRAL TO CHARGED PRODUCTION RATIO.