Small angle (≈3°) scattering of GeV photons from carbon and tungsten has been measured. The results are compared with the predictions of a simple “optical theorem” model, where the total cross-section for photon absorption is taken to be the incoherent sum of absorption on single nucleons.
Only stattistical errors are presented.
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The Λ p å Λ p cross section has been measured in the Λ-momentum range of 120 to 320 MeV/ c using 238 events. A comparison with the effective range approximation yielded the values a s = −2.46, a t = −2.07, r s = 3.87 and r t = 4.50 in fm.
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Total cross sections have been measured for H, He, 6 Li, C, O and Pb targets for 1 GeV incident energy protons. From the differential elastic scattering data published elsewhere, we also obtain the total elastic scattering and reaction cross sections for H, He, C and O. When our data are combined with other measurements in the same energy region, it is found that the total and reaction cross sections can be fit by the formulae σ T = 47 A 0.82 and σ R = 42 A 0.67 mb. It is also observed that the total and reaction cross sections for negative pions on nuclei can also be fit with these same A -dependencies.
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The cross sections for π + π − , K + K − , and K 0 K 0 final states from 2.7 GeV/ c p p interactions are: 28±9 γ b, 3 +6 −3 γb, and < 10 γb respectively. Angular distributions are presented and discussed.
Axis error includes +- 0.0/0.0 contribution (?////Due to contamination by other final states).
The momentum spectrum of 4 He produced at 0 o lab. by deuteron collisions at 1.69 GeV/ c , has been measured to determine possible π-π resonances of low effective mass values. No significant deviations from phase space are found. The total cross sections for the reaction d + d → 4 He + 2π is found to be (0.6±0.2) × × 10 −30 cm 2 .
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The ratio R = σ (e + + p)/ σ (e − + p) of the elastic scattering cross-section detecting the recoil proton at 0 o in coincidence with the backward electron or positron was found to be R = 1.036 ± 0.018 at q 2 = 8 fm −2 , R = 1.079 ± 0.046 at q 2 = 32 fm −2 .
Axis error includes +- 0.0/0.0 contribution (?////Errors presented are the total combined statistical and systematic error s. Radiative corrections applied).
Axis error includes +- 0.0/0.0 contribution (?////Errors presented are the total combined statistical and systematic error s. Radiative corrections applied).
The cross section and forward-backward muon charge asymmetry for the e + e − → μ + μ − γ reaction were measured to be σ =2.82±0.35 pb and A =−0.34±0.10 with the VENUS detector at TRISTAN at 〈√ s 〉=59.2GeV for an integrated luminosity of 53.5 pb −1 . The measured cross section agrees with the theoretical prediction. The asymmetry result is consistent with the electroweak prediction but not with the QED prediction at the level of 2 σ .
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The 4 He( γ ,p) 3 H reaction cross section has been measured with tagged photons of energy 81–158 MeV. Protons were detected over the angular range 55°–125°. The scaling of the data as a function of momentum mismatch has been examined for two reaction models, the modified quasideuteron mechanism and quasifree knockout. Both models show clear scaling behaviour but comparison of the predicted and measured scaling function shapes favours the modified quasideuteron mechanism at momenta up to ≈500 MeV/ c .
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