Differential cross sections for the elastic scattering of negative pi mesons on protons (π−−p→π−−p) were measured at the Berkeley Bevatron at five laboratory kinetic energies of the pion between 500 and 1000 MeV. The results were least-squares fitted with a power series in the cosine of the center-of-mass scattering angle, and total elastic cross sections for π−−p→π−−p were obtained by integrating under the fitted curves. The coefficients of the cosine series are shown plotted versus the incident pion laboratory kinetic energy. These curves display as a striking feature a large value of the coefficient of cos5θ* peaking in the vicinity of the 900-MeV resonance. This implies that a superposition of F52 and D52 partial waves is prominent in the scattering at this energy, since the coefficients for terms above cos5θ* are negligible. One possible explanation is that the F52 enhancement comes from an elastic resonance in the isotopic spin T=12 state, consistent with Regge-pole formalism, and the D52 partial-wave state may be enhanced by inelastic processes. At 600 MeV the values of the coefficients do not seem to demand the prominence of any single partial-wave state, although the results are compatible with an enhancement in the J=32 amplitude. A table listing quantum numbers plausibly associated with the various peaks and "shoulders" seen in the π±−p total cross-section curves is presented.
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NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The cross section for photoproduction of neutral pions from protons has been measured at energies near 750, 915 and 1150 Mev and over most of the forward-going [...] C.M. hemisphere. The experimental technique consisted of detecting both of the [...] decay photons with lead glass total absorption counters and, when convenient, the recoil proton with a single scintillation counter. The method is subject to rather large systematic errors but, within these, our results are consistent with other experiments wherever there are overlapping points. Our data has the striking feature that the cross section is very small at [...] in the region of the second and third pion nucleon resonances. Also, although the data is not inconsistent with a simple first, second and third resonance model, it appears likely that above the third resonance the pole process consisting of the exchange of a single vector meson is becoming important or even dominant. The evidence at this time mildly suggests that this behaviour is largely due to [...] mesons and under that hypothesis we are able to estimate some [...] meson coupling constants. For example, using a prescription of Gell-Mann and Zachariasen, we estimate the partial width for the decay [...] to be 240 Kev.
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Total (π+, p) and (p, p) cross sections in the momentum range 1.4 to 4.0 Bev/c are presented. These measurements, with an accuracy of approximately 2%, were made at the Berkeley Bevatron by using counter techniques. Pions were distinguished from protons by means of a gas-filled Čerenkov counter. The (π+, p) total cross section was found to be almost constant above 2.0 Bev/c at a value near 29 mb. The (p, p) cross section decreases gradually from 47.5 mb to 41.7 mb over the momentum range covered. Transmission measurements of π+-nucleus and p-nucleus cross sections in both good and poor geometry were made at 3.0 Bev/c. The results are compared with the predictions of the optical model. In contrast to most previous work at high energies, an essentially exact solution of the wave equation for a potential well with a diffuse edge was used. The values of the imaginary part of the optical potential that best fit the experimental data are in good agreement with the predicted values. No strong conclusion regarding the real part of the potential was possible. Absorption and total elastic scattering cross sections for Be, C, Al, and Cu are presented. The total elastic scattering cross sections from this experiment disagree with Wikner's for π−-nucleus scattering.
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