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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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The π−p elastic scattering differential cross section has been obtained at 18 incident momenta from 1.71 to 5.53 GeV/c. The measurements were taken over a limited range of squared four-momentum transfer t near the forward direction. The statistical accuracy and resolution of these data are comparable to, or better than, existing data. The parameter b in the expression dσdt=Aebt has been determined at each of our incident momenta, and a large (∼25%) enhancement in b as a function of momentum is observed at a c.m. energy of ∼2290 MeV. The relation of this bump in b with the well-established bump in the total π−p cross section at ∼2200 MeV is discussed.
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Measurements have been made on Compton scattering for photon energies between 5 and 17 GeV and t values from -0.06 to -1.1 (GeVc)2. The data were obtained by performing a coincidence between the Stanford Linear Accelerator Center 1.6-GeVc spectrometer and a Lucite shower counter. The scattering appears diffractive out to high t values, but the cross sections seem not to be in good agreement with the prediction of a strict vector-meson-dominance model.
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Results of a measurement of the π−p charge-exchange process at backward angles are presented. Differential cross sections were measured in the angular region −0.5<cosθ*<−1.0 at incident momenta of 2, 3, 4, 5, and 6 GeV/c. An additional background subtraction to a version of the data published previously has a significant effect at 6 GeV/c and brings the data into agreement with more recent measurements. The 6-GeV/c data were combined with existing measurements of the differential cross sections for backward π+p and π−p elastic scattering to yield values for the isotopic-spin-½ and −32 u-channel and s-channel amplitudes for backward pion-nucleon scattering and for the magnitude of the phases between them. It is found that the u-channel amplitudes can be explained by pure Regge-pole (Δδ, Nα) exchange only near the extreme backward direction, but that a Reggeized absorption model agrees at least qualitatively with the data. The phase difference between the I=12 and 32 s-channel amplitudes is approximately 90° over the region −0.8<u<0 (GeV/c)2.
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We have measured ρ0, ω (combined) and ϕ electroproduction over a range of virtual-photon four-momentum Q2 from 0.4 to 2.2 GeV2 and for photon energies ν from 2.7 to 8.6 GeV. We find that the slope of the t (momentum transfer) dependence of the ρ0 and ω forward peak decreases with increasing Q2 to less than half of the photoproduction slope.
The cross section for virtual photon are derived from E- P cross section bydividing on the virtual-photon flux factor.
We have measured the polarization parameter in neuton-proton charge-exchange scattering for incident neutron momenta of 2-12 GeVc and 0.01<~|t|<~1.0 (GeVc)2. Results based on 300 000 events show a negative polarization whose magnitude increases monotonically with |t| approaching 60% for |t|∼0.6 and which has little energy dependence.
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