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Differential cross sections for the reaction π−p→π0n were measured at nine incident-pion kinetic energies in the interval from 500 to 1300 MeV. The negative pion beam from the bevatron was focused on a liquidhydrogen target completely surrounded by a cubic array of six steel-plate spark chambers. The spark chambers were triggered on events with neutral final states. Charge-exchange events were identified from the one-shower and two-shower events in the spark-chamber pictures. By the Monte Carlo technique, the π0 distributions were calculated from the bisector distributions of the two-shower π0 events together with the observed γ-ray distributions of the one-shower π0 events. These π0 distributions were fitted with both Legendre-polynomial expansions and power-series expansions by the method of least squares. The extrapolated forward differential cross sections are in good agreement with the dispersion calculations. The Legendre coefficients for the differential cross sections in isospin state T=12 were obtained by combining our results with available data on π±p elastic scattering. In the light of existing phase-shift solutions, the behavior of these coefficients is discussed. The D5F5 interference term that peaks near 900 MeV is verified to be in isospin state T=12 only. We report here also the total neutral cross sections and the cross sections for the production of neutral multipion final states 2π0n and 3π0n. The 4π solid angle and the calibrated energy response of the spark chambers contribute to the accuracy of the results.
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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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Differential cross sections for the elastic scattering of positive pi mesons by protons were measured at the Berkeley Bevatron at pion laboratory kinetic energies between 500 and 1600 MeV. Fifty scintillation counters and a matrix coincidence system were used to identify incoming pions and detect the recoil proton and pion companions. Results were fitted with a power series in the cosine of the center-of-mass scattering angle, and total elastic cross sections were obtained by integrating under the fitted curves. The coefficients of the cosine series are displayed, plotted versus the laboratory kinetic energy of the pion. The most striking features of these curves are the large positive value of the coefficient of cos6θ*, and the large negative value of the coefficient of cos4θ*, both of which maximize in the vicinity of the 1350-MeV peak in the total cross section. These results indicate that the most predominant state contributing to the scattering at the 1350-MeV peak has total angular momentum J=72, since the coefficients for terms above cos6θ* are negligible at this energy. One possible explanation is that the 1350-MeV peak is the result of an F72 resonance lying on the same Regge-pole trajectory as the (32, 32) resonance near 195 MeV.
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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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Total cross sections of π+ and π− mesons on protons and deuterons have been measured in a transmission experiment to relative accuracies of ±0.2% over the laboratory momentum range 0.46-2.67 GeV/c. The systematic error is estimated to be about ±0.5% over most of the range, increasing to about ±2% near both ends. Data have been obtained at momentum intervals of 25-50 MeV/c with a momentum resolution of ±0.6%. No new structure is observed in the π±p total cross sections, but results differ in several details from previous experiments. From 1-2 GeV/c, where systematic erros are the smallest, the total cross section of π− mesons on deuterons is found to be consistently higher than that of π+ mesons by (1.3±0.3)%; about half of this difference may be understood in terms of Coulomb-barrier effects. The πd and πN total cross sections are used to check the validity of the Glauber theory. Substantial disagreements (up to 2 mb) are observed, and the conclusion is drawn that the Glauber theory is inadequate in this momentum range.
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The total cross sections for νμn and νμp charged-current interactions and their ratio R=σT(νn)σT(νp) have been measured as a function of neutrino energy from 0.4 to 10 GeV. The experiment is performed using the BNL 7-foot deuterium bubble chamber exposed to the Alternating Gradient Synchrotron wide-band neutrino beam. The absolute values of the cross sections are normalized to the quasielastic scattering (νμn→μ−p) cross section. Above 1.6 GeV the data are consistent with the quark-parton model. We find that σT(νn)Eν=(1.07±0.05)×10−38, σT(νp)Eν=(0.54±0.04)×10−38, and σT(νN)Eν=(0.80±0.03)×10−38 cm2/GeV for 〈Eν〉=3.2 GeV, and R=1.95±0.10 for 〈Eν〉=3.7 GeV.
Axis error includes +- 0.0/0.0 contribution (?////SYSTEMATIC ERROR NOT GIVENNEUTRAL CURRENT AND NEUTRAL PARTICLES INDUCED REACTIONS, RESCATTERING IN DEUTERIUM).
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The total and differential cross sections of the K¯0p→Λπ+ and K¯0p→∑0π+ reactions have been measured in the centre-of-mass energy range of l.5 to 2.3 GeV. Using our K¯0p→∑0π+ data as well as available cross-section data of isospin related channels, we have calculated the total I=0K¯N→∑π cross section as function of energy. The results are compared with predictions obtained from K¯N phase-shift analyses.
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Results are presented of differential cross-section measurements for the reaction π − p→ π 0 n; π 0 → γγ at 22 incident pion momenta between 618 and 2724 MeV/ c . The results are in good agreement with those of other experiments. They represent the first comprehensive set of high statistics measurements of the π − p charge-exchange differential cross section at closely spaced momenta in the resonance region.
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