Title page for ETD etd-10042006-143839


Type of Document Dissertation
Author Lai, Anzhi
URN etd-10042006-143839
Title Bhabha scattering in e+e- collisions at TRISTAN
Degree PhD
Department Physics
Advisory Committee
Advisor Name Title
Abashian, Alexander Committee Chair
Bowden, Robert L. Committee Member
Chang, Lay Nam Committee Member
Gotow, Kazuo Committee Member
Piilonen, Leo E. Committee Member
Keywords
  • Interacting boson-fermion models
  • Polarization (Nuclear physics)
  • Thermal neutrons Scattering.
Date of Defense 1992-05-05
Availability restricted
Abstract

Bhabha scattering, the process of e+ e- ⟶ e+ e- , has been studied at center-of-mass energies from 50 to 58 GeV with the AMY detector at the KEK e+e- storage ring TRISTAN. The study is based on a data sample of 79.7 pb-1 integrated luminosity. The differential cross section of Bhabha scattering has been measured. The measured cross section is found to agree fairly well with the Standard Model of the electroweak theory. The measured cross section is also compared with various four-fermion contact interaction models, and confidence level lower limits on the composite scale, A, are determined. In addition, the limits on VV model are converted to SM-break-down scales, which indicate the validity of the SM down to the distance of order ~ 10-17 cm and the electron charge radius of ~ 10-16 cm. Attempts are made in searching for an additional boson Z'. No clear signal of the existence of a Z' boson is found up to energy of ~160 GeV/c2. The effect of transverse beam polarization on Bhabha scattering is also studied. The ∅ dependence of Bhabha events are fitted to the QED prediction and found to agree with the theory. However, no quantitative conclusion on polarization effect can be drawn based on current data sample, which does not provide enough statistics. More data is being accumulated and further study should be carried out.

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