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Final results are presented from a spark-chamber experiment performed at the Princeton-Pennsylvania Accelerator to measure the differential cross section near 0° for the reaction π−p→π0n. The data are extrapolated to 0° and the results of the extrapolation are compared with the results of other experiments and with dispersion relation predictions. The values of the forward-scattering amplitude for the fifteen values of incident π− momentum at which measurements were made are as follows: (p (MeV/c), (dσdΩ)0° (mb/sr)): (561,3.28), (636,2.95), (687,3.38), (750,2.48), (802,1.33), (930,2.42), (1005,3.15), (1030,3.43), (1077,1.70), (1134,1.04), (1434,0.31), (1579,0.56), (1711,0.73), (1914,0.87), (2106,0.56). The combined statistical and systematic uncertainties in these values is about ±9%. A description of the apparatus, a discussion of the methods of analysis, and a discussion of the errors contributing to the uncertainties in the above results are included in the text.
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Elastic electron-proton scattering cross sections have been measured using the internal beam of the 6-BeV Cambridge Electron Accelerator at laboratory scattering angles between 31° and 90° for values of the four-momentum transfer squared ranging from q2=0.389 to 6.81 (BeV/c)2 (q2=10 to 175F−2). Incident electron energies ranged from 1.0 to 6.0 BeV. Scattered electrons from an internal liquid-hydrogen target were momentum-analyzed using a single quadrupole spectrometer capable of momentum analysis up to 3.0 BeV/c. Čerenkov and shower counters were used to help reject pion and low-energy background. The cross sections presented are absolute cross sections with experimental errors ranging from 6.8% to 20%. Separation of proton electromagnetic form factors have been made for all but the two highest momentum transfer points, using the Rosenbluth formula. Both form factors, GEp and GMp, were observed to continue to decrease as the momentum transfer increases. An upper limit to the possible asymptotic values of the proton electromagnetic form factors has been established.
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Using the internal beam of DESY elastic electron-proton cross-sections were measured at various angles between 32° and 130°, and with momentum transfers ofq 2=39, 60, 80 and 110 fm−2. Two single-quadrupole spectrometers, movable around a common liquid-hydrogen target, were used for analysing the momentum of the scattered electrons. Čerenkov and shower counters discriminated against pion and low-energy background. As a cross-section reference, recoil protons from elastic scattering atq 2=10 fm−2 were used, with a quantameter serving as an intermediate monitor. The data are consistent with the Rosenbluth formula, giving real form factorsG E andG M . Both continue to decrease with increasing momentum transfer, but somewhat faster than indicated by measurements performed so far.
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Photoproduction of $\Lambda$(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8/LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K$^{+/0}$ angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K$^+$ angles.
The measured differential cross sections from the liquid hydrogen target, protons, as a function the K+ polar angle.
The measured differential cross sections from the liquid hydrogen target, protons, as a function the photon energy at forward K+ polar angles of 19-43 degrees .
The measured of differential cross section at backward K+/K0 polar angles of 120-150 degrees as a function of photon energy from the liquid hydrogen target, protons, and liquid deuterium target, deuterons.
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Total p−p cross-section measurements have been made at 28 momenta, in the range (0.575÷5.35) GeV/c. The cross-section decreases monotonically with increasing momentum. No important irregularity has been found.
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We have studied neutral final states produced in π−p collisions at momenta of 1.71, 1.89, 2.07, 2.27, and 2.46 GeVc, by observing the γ rays emitted. In particular, measurements are presented of (i) π−p→π0n, for which the Regge-pole fit at momenta ≥5.9 GeVc also agrees rather well here; (ii) π−p→η0n, for which the Regge model which fits at higher energies does not agree here; (iii) π−p→π0γn, in which there is some evidence for a diffraction dissociation process as well as ω0-meson production; (iv) π−p→π0π0n, which is dominated by production of N*0(1236)π0 and by peripheral production of pion pairs. In (iv), the former process is found to fit with the same Reggeized ρ-meson exchange model as charge-exchange scattering, while the latter gives indication of the s-wave ππ interaction. An account is given of new techniques, particularly in the data analysis, which were developed in the course of this work.
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