Measurements of the Mass of the W Boson in the W+W- → qq¯qq¯ Channel With the ALEPH Detector

Chalmers, Matthew Donald Kennedy (1999) Measurements of the Mass of the W Boson in the W+W- → qq¯qq¯ Channel With the ALEPH Detector. PhD thesis, University of Glasgow.

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Abstract

A measurement of the mass of the W boson from e+e- → W+W- → qq¯qq¯ events is presented, from LEP data collected at √s= 189 GeV during 1998 with the ALEPH detector. The procedure of direct reconstruction of the W+W- final state invariant mass distribution is adopted, with an optimisation of the event selection and jet clustering algorithms. A two dimensional Monte Carlo reweighting technique is used to extract the W mass and a full discussion of the systematic uncertainties is given. The W mass is measured to be: MW = 80.556 +/- 0.110(stat.) +/- 0.039(syst.) +/- 0.056(F.S.I.) +/- 0.017(LEP) GeV/c2. A new technique for extracting the W mass using a two dimensional Kolmogorov Smirnov test is introduced. The W mass using this method is measured to be: MKSW = 80.423 +/- 0.160(expected stat.) GeV/c2, which is compared with that from the method of maximum likelihood. Rigorous optimisation and stability checks on the W mass estimator and its error are presented, and the result put into the context of a LEP and subsequently world average value: MworldW = 80.394 +/- 0.042 GeV/c2. The implications of this result are interpreted by comparing it with the indirect W mass measurement from the Standard Model prediction: MindirectW = 80.381 +/- 0.026 GeV/c2. A discussion and outlook for the W mass measurement at LEP is given.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Jason Ward
Keywords: High energy physics, Theoretical physics
Date of Award: 1999
Depositing User: Enlighten Team
Unique ID: glathesis:1999-76346
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 15:23
Last Modified: 19 Nov 2019 15:23
URI: http://theses.gla.ac.uk/id/eprint/76346

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