The π − p differential elastic scattering cross sections have been measured for eight momenta in the 33–55 GeV/ c range. The energy dependence of the slope and of the total elastic scattering cross sections has been determined experimentally. The results are compared with the known data. The experimental data are compared both with the Regge pole model and with the quasi-potential one.
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Elastik K − n ( I = 1) differential cross sections have been measured at 14 momenta between 610 and 940 MeV/ c , over the c.m. angular range −0.7 < cos θ ∗ < 0.8 . The results, which cover the c.m. energy range 1610–1765 MeV, have been fitted with Legendre polynomials and compared with some existing predictions from a partial-wave analysis.
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We present results from a high-momentum-resolution measurement of the π-p elastic differential and total cross-sections-at values of cos θ* between — 0.60 and 0.85 in the centre-of-mass system and at incident-beam momenta between 1.34GeV/c and 1.49 GeV/c—close to the X0 production threshold. There is no significant enhancement near the X0 production threshold. However, a small effect of ~ 3 standard deviations is present, having mass 1898.8 MeV and width ~5MeV, and appearing at an incident-pion momentum of 1435 MeV/c. In addition, a narrow ~ 5-standard-deviation effect atEc.m.= 1876 MeV appeared at an incident-pion momentum of 1389 MeV/c.
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Elastic π+−p scattering at 1.1 Bev and elastic p−p scattering at 582 Mev have been measured using a propane bubble chamber. On the basis of 661 identified π+−p elastic scatterings found in the scanning of 1.726×106 cm of pion track, the total elastic cross section is found to be 12.3±1.2 mb. The differential cross section is rather isotropic at large angles and exhibits a strong peak for small forward scattering angles. If the forward peak is interpreted as diffraction scattering according to the optical model, the data are best fitted by a proton with a π+−p interaction radius, R=(0.99−0.11+0.13)×10−13 cm and an opacity, O=0.70−0.07+0.06. The total cross section for p−p elastic scattering at 582 Mev was found to be 24.2±1.6 mb on the basis of 2442 elastic scatterings observed in the scanning of 3.000×106 cm of proton track. Both differential and total p−p cross sections are in excellent agreement with the results of counter experiments in this energy region.
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A bubble chamber investigation of π−+p elastic scattering at 1 200 MeV (K.E.) is reported. The total and differential cross-sections are determined. By extrapolation of the angular distribution, the 0° cross-section is derived and compared with the results obtained with the help of the dispersion relations and the optical theorem. The forward peak is investigated in terms of diffraction scattering and a value for the optical radius is derived.
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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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Total and differential elastic cross-section data are presented at eight incident π+ momenta: 1.28, 1.34, 1.40, 1.43, 1.55, 1.68, 1.77, and 1.84 GeVc. These data were obtained from a hydrogen-bubble-chamber exposure at the Bevatron, and contain more than 65 000 events. This represents more than 1½ times the world's data hitherto available in this energy region.
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We measured elastic-scattering angular distributions for π++p scattering at 1.5, 2.0, and 2.5 BeV/c using spark chambers to detect scattered pions and protons. A bump that decreases in amplitude with increasing momentum is observed in the backward hemisphere in the 1.5- and 2.0-BeV/c distributions, but is not observed in the 2.5-BeV/c distributions. It appears reasonable to attribute this phenomenon to the 1.45-BeV/c resonance observed in the π++p total cross section. The data are compared with π−+p data and are found to support the theoretical prediction that the scattering cross sections for both charge states should become equal at high energies. We fit the angular distributions with a power series in cosθ*, and compare the extrapolated values for the scattering cross section in the backward direction with the calculation of the neutron-exchange pole contribution to the cross section. The "elementary" neutron-pole term contribution is calculated to be 90 mb/sr at 2.0 BeV/c, in violent disagreement with the extrapolated value, ≈0.5 mb/sr.
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Differential cross sections for π+p elastic scattering in the momentum region 1.2 to 2.3 GeV/c are presented for the center-of-mass angular range 0.9>cosθ>−0.9. Typically, 50 000 events were obtained at each of 16 momenta using magnetostrictive-readout wire spark chambers to detect the particles scattered from a liquid hydrogen target. The results are compared to those of the CERN-71 phase-shift analysis. The well-known dips at t≅−0.7 (GeV/c)2 and at u′=−0.2 (GeV/c)2 are observed. In addition, structure is seen at constant u′=−1.3 (GeV/c)2. The results of a pion attenuation study in iron are also presented.
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