Authors:	Adam, Lennart
Title:	Precision Matters: Measurement of the W boson mass and width with the ATLAS detector at a centre-of-mass energy of 7 TeV and the activity of the Underlying Event in Z boson events at a centre-of-mass energy of 13 TeV
Other Title:	Precision Matters: Measurement of the W boson mass and width with the ATLAS detector at √s = 7 TeV and the activity of the Underlying Event in Z boson events at √s = 13 TeV
Online publication date:	23-Feb-2021
Year of first publication:	2021
Language:	english
Abstract:	The Standard Model is today the most powerful theory to describe and predict the behaviour and quantities of elementary particles. A set of free parameters are not directly predicted, but linked via quantum physics relations to other quantities of the Standard Model. Precise measurements of these parameters are therefore crucial to probe the Standard Model and serve as a test of its consistency. The mass of the W boson plays a key role among these parameters, because the theoretical prediction currently outperforms the precision of its experimentally measured value. It is therefore a natural target to probe for a possible tension, which could yield hints to new physics. This thesis presents an improved measurement of the mass of the W boson with the ATLAS detector at a centre-of-mass energy of 7 TeV. The legacy ATLAS measurement is re-evaluated using a profile likelihood ratio fit. An improvement of about 2 MeV on the uncertainty is accomplished and sets the path for the target precision. The introduced fit method enhances the sensitivity of the measurement and allows a first determination of the decay width of the W boson with LHC data. The precision of the width measurement is compatible to the current world average and provides an additional parameter for the consistency tests. The second part of this thesis presents measurements of charged-particle distributions sensitive to the properties of the underlying event in events containing a Z boson decaying into a muon pair at a centre-of-mass energy of 13 TeV. The measurement is a standard candle for hadron-colliders and serves as ancillary measurement for the future measurement of the mass of the W boson. The measured distributions provide crucial feedback to the tested Monte Carlo generators, which will in turn promote the measurement of the transverse momentum of the W boson.
DDC:	500 Naturwissenschaften 500 Natural sciences and mathematics 530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-5652
URN:	urn:nbn:de:hebis:77-openscience-35e0df0e-f38d-4a86-b008-536d29dc86a35
Version:	Original work
Publication type:	Dissertation
License:	CC BY-ND
Information on rights of use:	https://creativecommons.org/licenses/by-nd/4.0/
Extent:	211 Seiten
Appears in collections:	JGU-Publikationen