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Title: A measurement of the cross section for e⁺e⁻ → e⁺e⁻ and e⁺e⁻ → e⁺e⁻γ at high energy
Author: Illingworth, John
ISNI:       0000 0001 3586 3381
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1983
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Data from the TASSO experiment at the PETRA e+e- storage ring has been analysed to investigate the cross section for the QED reactions (a)e+e- → e+e- Bhabha scattering and (b)e+e- → e+e- + γ. Details of the TASSO detector and a detailed description of an array of lead/scintillator sandwich electromagnetic shower counters, used in the analysis of reaction (b), is given. For beam energies greater than 10 Gev the ratio of the measured total Bhabha scattering cross section to the QED prediction was found to be 0.949 ±0.013 (statistical) ±0.06(systematic). It was shown, by fitting the measured angular cross section, that QED is a point like theory down to distances of 2x10-18 m. The predictions of models of electroweak unification have been compared to the data and parameters of these theories have been found to agree with, but not strongly constrain, these theories. Significant limits are placed on electroweak theories which predict more than 1 neutral weak gauge boson. The number of events with two charged tracks and one photon has been measured and compared to the QED cross section predictions for reaction (b). 21 such events were selected and this agrees well with the predicted number of 25±2.6. The agreement of these numbers has been used to determine that the mass of an excited electron state, e*, (which would contribute events to this experimental signature by its radiative decay) must be greater than 34 Gev (95% confidence limit), if it has normal couplings.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Nuclear physics & particle accelerators