Polarization and differential cross-section data for elastic scattering of positive pions on protons between 0.82 and 2.74 GeV/ c are presented. A dip in the polarization, at constant u ≈ −0.65 GeV 2 , is observed. The data are compared with published phase-shift analyses.
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Invariant single-particle cross sections for pion and proton production in π ± p interactions at 8 and 16 GeV/ c are presented in terms of integrated distributions as functions of x , reduced rapidity ζ and p ⊥ 2 , and also in terms of double differential cross sections E d 2 σ /(d x d p ⊥ 2 ) and d ζ d p ⊥ 2 ). A comparison of π ± and π − induced reactions is made and the energy dependence is discussed. It is shown that the single-particle structure function cannot be factorized in its dependece on transverse and longitudinal momentum. For the beam-unlike pion, there is an indication for factorizability in terms of rapidity and transverse momentum in a small central region.
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The c.m. angular distribution of π+p elastic scattering at 1.6 GeV/c shows a strong forward diffraction peak decreasing exponentially with a slopeA + = (6.9±0.5) GeV−2 comparable to thatA − = (7.2±0.5) GeV−2 observed in a previous experiment for π-p elastic scattering at the same incident momentum. The behaviour of the π+ and the π− angular distributions is quite different beyond the diffraction peak. The π+p total elastic cross-section is found to be Σ01 = (16.70±0.45) mb.
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The Fermilab hybrid 30-in. bubble-chamber spectrometer was exposed to a tagged 147-GeV/c positive beam containing π+, K+, and p. A sample of 3003 K+p, 19410 pp, and 20745 π+p interactions is used to derive σn, 〈n〉, f2cc, and 〈nc〉D for each beam particle. These values are compared to values obtained at other, mostly lower, beam momenta. The overall dependence of 〈n〉 on Ea, the available center-of-mass energy, for these three reactions as well as π−p and pp interactions has been determined.
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We present results of measurements of the differential cross sections for the following elastic-scattering reactions: (i) π + p at 5.2 and 7.0 GeV/ c in the range −1 < u < 0.02 (GeV/ c ) 2 , (ii) π − p at 7.0 GeV/ c in the range −0.7 < u < 0.05 (GeV/ c ) 2 , (iii) K + p at 5.2 and 7.0 GeV/ c in the ranges −1 < t < −0.01 (GeV/ c ) 2 and −1 < u < 0 (GeV/ c ) 2 , and K − p at 7.0 GeV/ c in the range −1 < u < 0 (GeV/ c ) 2 .
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SIDE GEOMETRY.
The angular distributions of K + p and π + p backward elastic scattering have been measured at 5.2 and 6.9 GeV/ c . Backward π - p and K - p elastic scattering were studied at 6.9 GeV/ c . Backward peaks are observed in K + p scattering with an energy dependence of the form s −4 .
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The polarization and the differential cross section in π−p elastic scattering have been measured at incident pion laboratory momenta of 1.70, 1.88, 2.07, 2.27, and 2.50 GeV/c. The experiment was carried out at the Argonne zero-gradient synchrotron with a polarized proton target. Details of the apparatus and data analysis are presented here together with the final results. A partial-wave analysis of the data has verified the JP=72+ assignment for the Δ(1950) and established a JP=72− assignment for the N(2190). It does not support a JP=112+ assignment for the Δ(2460), nor does it give support for some of the possible resonances found in the CERN phase-shift analysis. Apart from the resonance behavior, the partial-wave analysis reveals several new features. We find a striking correlation among the various partial-wave amplitudes at the highest energy, which is different for J=l+12 and J=l−12. In addition, several fixed-(−t) features of high-energy scattering emerge in the energy region of this analysis.
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The differential cross-section for 5 GeV/ cπ + p and π − p elastic scattering have been measured in the c.m. angular region 27° < θ cm < 130° corresponding to 0.5 < | t | < 7.8 (GeV/ c ) 2 . Dips are observed in both reactions at − t = 2.8 and 4.8 (GeV/ c ) 2 where the cross-sections are approximately 0.1 μ b/(GeV/ c ) 2 .
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We have measured π+p, π−p, and pp elastic scattering at an incident-beam momentum of 200 GeV/c in the region of −t, four-momentum transfer squared, from 0.021 to 0.665 (GeV/c)2. The data allow an investigation of the t dependence of the logarithmic forward slope parameter b≡(ddt)(lndσdt). In addition to standard parametrization, we use functional forms suggested by the additive quark model to fit the measured dσdt distributions. Within the context of this model we estimate the size of the clothed quark in the pion and proton. Limits on the elastic-scattering amplitude derived from unitarity bounds are checked, and no violations are observed.
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A description is given of an experiment to study elastic scattering of π ± , K ± and p on protons at c.m. scattering angles from 45° to 100° at incident laboratory momenta 20 GeV/ c and 30 GeV/ c . The corresponding t range is from −6.2 (GeV/ c ) 2 to −28 (GeV/ c ) 2 . There are no previous observations for these reactions in this t range. High intensity and large geometrical acceptance were required in order to measure the low cross sections. The experiment used a double-arm spectrometer. MWPCs were used for reconstruction, and threshold and differential Čerenkov counters for identification. Scintillation counters, Čerenkov counters and a hadron calorimeter were used in the trigger. The trigger logic utilized specially designed matrices and a hard wired microprocessor. The π − p elastic scattering cross sections follow approximately the dimensional counting rule from 3.5 GeV/ c .and up to 30 GeV/ c . The cross sections decrease by seven orders of magnitude in this energy range. The data is compared to quark models. None of these models give a comprehensive description of the results. However, some modifications to these models improve their consistency with the data.
EARLIER RESULTS GIVEN IN 'A'.
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