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The present PETRA experiments on Bhabha scattering, lepton-pair production and two-photon annihilation are consistent with exact QED up to ]q2I ≈ 1000 GeV2. Lower bounds on the cut-off parameters Λ exceed 100 GeV which is equivalent to tests of QED down to distances < 2 · 10-1a cm. Electro-weak interference effects become sizeable at the highest PETRA energies. Further tests of QED up to LEP energies...
The measurement of the anisotropy in the quenching radiation emitted by metastable hydrogenic systems in an electric field can be used to determine the Lamb shift. This approach was conceived as a method for the measurement of Lamb shift in high-Z ions but was tested on H, D and He+ where high precision Lamb shift values are available both from theory and from earlier experiments. After a brief...
The positron production yields in close ion-atom collisions have been investigated for the U+Cm, U+U and U+Pb scattering systems at U beam energies between 4.7 and 5.9 MeV/u. Furtheron positron spectra were measured for the overcritical U+U and the undercritical U+Pb system at 5.9 MeV/u and a scattering angle 8LabIon = 45°±10° . All positron yields, including earlier measurements, follow...
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