Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

First Advisor

Roger R. McNeil

Abstract

This dissertation describes the measurement of the forward-backward charge asymmetry, A$\sb{\rm b}$, for e$\sp{+}$e$\sp{-} \to$ bb at TRISTAN by the AMY detector. A measurement of the ratio, R$\sb{\rm b}$, of the cross section for e$\sp{+}$e$\sp{-} \to$ bb to the theoretical QED cross section for e$\sp{+}$e$\sp{-}\ \to\ \mu\sp{+}\mu\sp{-}$ is also obtained. A$\sb{\rm b}$ is an effect of the weak-electromagnetic interference. The measurement of A$\sb{\rm b}$ is therefore a direct test of the standard model electroweak theory. TRISTAN is the only e$\sp{+}$e$\sp{-}$ collider in the world to explore the center-of-mass energy region of 50 GeV to 62 GeV, where the effects of weak-electromagnetic interference becomes maximum. The data were collected between June 1987 and July 1989 with a total integrated luminosity of 33.3 pb$\sp{-1}$ and center-of-mass energies ranging from 52 GeV to 61.8 GeV. Multihadronic events with a muon were used for the analysis. The measured values were A$\sb{\rm b}$ = $-$0.82 $\pm$ 0.25(stat) $\pm$ 0.14(syst) and R$\sb{\rm b}$ = 0.47 $\pm$ 0.12 $\pm$ 0.12 at an average center-of-mass energy of 57.2 GeV. These results were consistent with the standard model electroweak theory predictions of A$\sb{\rm b}$ = $-$0.58 and R$\sb{\rm b}$ = 0.56 at this energy. The measurement of the charge asymmetry is used to set a limit on B$\sp0-$B$\sp0$ mixing of $\chi\ <$ 0.20 at the 90% confidence level.

Pages

164

DOI

10.31390/gradschool_disstheses.4999

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