Placing limits on the Higgs production cross section at the tevatron using the H to W+W- to l+l- decay channel

Davies, Toby (2008) Placing limits on the Higgs production cross section at the tevatron using the H to W+W- to l+l- decay channel. PhD thesis, University of Glasgow.

Abstract

Limits on the Higgs production crosssection at the Tevatron were placed using data with an integrated luminosity of 2.4 fb−1 from CDF. Limits over a Higgs mass range between 110 GeV and 200 GeV were determined, by calculating a limit at ten mass points distributed over this region. The analysis exclusively searches for Higgs produced by top-quark mediated gluon fusion and then decaying in to two W bosons. Only leptonic decay channel software considered, such that the final event signature consists of ee, eu, or uu with missing energy from undetected neutrinos. After an evaluation of alternative techniques, a neural net was selected as the best method for increasing the sensitivity of the measurement. The BFGS neuralnet training technique was selected as the most efficient method. A Bayesian Likelihood technique was used to place limits on the observed Higgs production cross section, and an expected limit was calculated by running 10,000 pseudo experiments. The 160Ge V mass point was the most most sensitive, achieving an expected limit 4.1 times the Standard Model prediction cross sectionat a 95% Confidence Level. Observed limits are with in 1σ of the expected limit belowa mass point of 160 GeV. Above this, observed limits are higher than the expected limits, within 2σ. The lowest observed limit was also at MH=160 GeV with a limit of 6.85 times the Standard Model prediction at a 95% Confidence Level. A new method for increasing the sensitivity of the measurement was proposed and investigated, but unused in the analysis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Bussey, Mr. Peter
• Date of Award: 2008
• Depositing User: Mr Toby Davies
• Unique ID: glathesis:2008-806
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 01 Jul 2009
• Last Modified: 10 Dec 2012 13:26
• URI: https://theses.gla.ac.uk/id/eprint/806