| dc.contributor.advisor | Quadt, Arnulf Prof. Dr. | |
| dc.contributor.author | Kareem, Mohammad Jawad | |
| dc.date.accessioned | 2017-04-28T08:10:27Z | |
| dc.date.available | 2017-04-28T08:10:27Z | |
| dc.date.issued | 2017-04-28 | |
| dc.identifier.uri | http://hdl.handle.net/11858/00-1735-0000-0023-3E2E-B | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-6277 | |
| dc.language.iso | eng | de |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/4.0/ | |
| dc.subject.ddc | 530 | de |
| dc.title | Measurement of the W Boson Helicity Fractions in Top/anit-Top Events at 8 TeV in the Lepton + Jets Channel with the ATLAS Detector | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Quadt, Arnulf Prof. Dr. | |
| dc.date.examination | 2017-04-20 | |
| dc.subject.gok | Physik (PPN621336750) | de |
| dc.description.abstracteng | Precise measurements of the properties of the top quark allow for testing the Standard
Model (SM) and can be used to constrain new physics models. The top quark is predicted
in the SM to decay almost exclusively to a W boson and b-quark. Thus, studying the
Wtb vertex structure at high precision and in detail is motivated.
This thesis presents a measurement of the W boson helicity fractions in top quark
decays with top/anit-top events in the lepton + jets final state using proton-proton collisions at
a centre-of-mass energy of 8 TeV recorded in 2012 with the ATLAS detector at
the LHC. The data sample corresponds to an integrated luminosity of 20.2 fb-1. The
angular distribution of two different analysers, the charged lepton and the down-type
quark in the W boson rest frame are used to measure the helicity fractions. The most
precise measurement is obtained from the leptonic analyser and events which contain at
least two b-quark tagged jets. The results of F0 = 0.709 ± 0.012 (stat.+bkg. norm.) +0.015 -0.014, FL = 0.299 ± 0.008 (stat.+bkg. norm.) +0.013
-0.012 and FR = -0.008 ± 0.006 (stat.+bkg. norm.) ±0.012 (syst.), which stand for longitudinal, left- and right-handed W boson helicity fractions respectively,
are obtained by performing a combined fit of electron+jets and muon+jets channels
to data. The measured helicity fractions are consistent with the Standard Model
prediction. As the polarisation state of the W boson in top quark decays is sensitive to
the Wtb vertex structure, limits on anomalous Wtb couplings are set. | de |
| dc.contributor.coReferee | Lai, Stan Prof. Dr. | |
| dc.subject.eng | Top Quark + Helicity Fractions + Anomalous Couplings + KLFitter | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-11858/00-1735-0000-0023-3E2E-B-7 | |
| dc.affiliation.institute | Fakultät für Physik | de |
| dc.identifier.ppn | 885276191 | |