Top cross section ratios as a test of lepton universality in charged weak decays in proton-proton collisions at \(\sqrt{s}\) = 7 TeV with the atlas detector

Palmer, Jody David (2014). Top cross section ratios as a test of lepton universality in charged weak decays in proton-proton collisions at \(\sqrt{s}\) = 7 TeV with the atlas detector. University of Birmingham. Ph.D.

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Abstract

In this thesis partial production cross sections of \({tṫ}\) events are measured in four channels, defined by the final state leptons from the decay of the \(W\) bosons and the triggering lepton, using ~5.6 fb\(^{-1}\) of data taken with the ATLAS detector at \(\sqrt{s}\) = 7 TeV. The di-lepton channel is defined as having one electron and one muon in the final state. The lepton plus tauchannels are defined as having a final state electron or muon and one hadronically decaying tau. Partial cross sections for these channels are estimated, and ratios of partial cross sections, defined with the same triggering lepton, are calculated. The di-lepton events are divided into two non-exclusive channels defined by the presence of a trigger matched lepton.
The production cross-sections of \(t\)\overline{t} events with final states including an electron and a hadronically decaying tau, or an electron and a muon, were measured and used to calculate their ratio \(R\)\(_{er}\) = 0.65\(_{-0.10}\)\(^{+0.12}\)(\(stat.\)) ± 0.18(\(syst.\)). The cross section ratio \(R\)\(_{er}\) measured in data is compared to that inferred from the world average \(W\) and tau branching fractions, \(R\)\(_{er}\)\(^{Data}\)/\(R\)\(_{er}\)\(^{PDG}\) = 1.1\(_{-0.17}\)\(^{+0.21}\)(\(stats.\)) ± 0.31(\(syst.\)) and is found to be consistent with unity.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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