A measurement of the helicity of <italic>W</italic> bosons produced in top -quark decays.
dc.contributor.author | Goldschmidt, Nathan J. | |
dc.contributor.advisor | Gerdes, David W. | |
dc.date.accessioned | 2016-08-30T15:49:59Z | |
dc.date.available | 2016-08-30T15:49:59Z | |
dc.date.issued | 2005 | |
dc.identifier.uri | http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:3186637 | |
dc.identifier.uri | https://hdl.handle.net/2027.42/125087 | |
dc.description.abstract | The Standard Model of particle physics is a remarkably successful description of nature. One aspect of the theory that is not well-understood is the nature and the origin of the mechanism which breaks the gauge symmetry of the electroweak interaction. According to the theory, this mechanism gives rise to the masses of elementary particles. However, we have yet to directly probe these phenomena. The top quark is the most massive known elementary particle; it decays almost exclusively via the electroweak interaction. By studying the kinematics of top-quark decays, we can indirectly probe the electroweak symmetry breaking mechanism at the highest energies presently attainable. We measure the fraction of longitudinally-polarized <italic>W</italic> bosons produced in top-quark decays by analyzing the transverse momentum spectrum of charged-lepton arising from the process <italic>t</italic> → <italic> W</italic><super>+</super><italic>b</italic> → ℓ<super>+</super>nu<sub> ℓ</sub><italic>b</italic>. Top-quark pairs are produced in proton-antiproton collisions with a center-of-mass energy s = 1.96 GeV at the Tevtron synchrotron at the Fermi National Accelerator Laboratory in Batavia Illinois. Top-quark candidate events are isolated in 200 pb<super>-1</super> of data using the newly-upgraded CDF II detector. These data indicate that the fraction of <italic>W</italic> bosons with longitudinal polarization is <italic>F</italic><sub>0</sub> = 0.88+0.12-0.47 (stat. + syst.), <italic>F</italic><sub>0</sub> > 0.24 95% CL in events where only one <italic>W</italic> decays leptonically; <italic>F</italic><sub> 0</sub> < 0.52 95% CL, <italic>F</italic><sub>0</sub> < 0.94 99% CL in events where both <italic>W</italic>'s decay leptonically, and <italic> F</italic><sub>0</sub> = 0.27+0.35-0.21 (stat. + syst.), <italic>F</italic><sub>0</sub> < 0.88 95% CL in the combined analysis. The Standard Model prediction, given a top-quark mass of 175 GeV, is <italic>F</italic><sub>0</sub> = 0.703. The discrepancy in the dilepton sample is suggestive of new phenomena, while the result in the single-lepton sample is fully consistent with the Standard Model expectation. Clearly, these results warrant further investigation. | |
dc.format.extent | 110 p. | |
dc.language | English | |
dc.language.iso | EN | |
dc.subject | Decays | |
dc.subject | Helicity | |
dc.subject | Measurement | |
dc.subject | Produced | |
dc.subject | Top Quark | |
dc.subject | W Bosons | |
dc.title | A measurement of the helicity of <italic>W</italic> bosons produced in top -quark decays. | |
dc.type | Thesis | |
dc.description.thesisdegreename | PhD | en_US |
dc.description.thesisdegreediscipline | High energy physics | |
dc.description.thesisdegreediscipline | Pure Sciences | |
dc.description.thesisdegreegrantor | University of Michigan, Horace H. Rackham School of Graduate Studies | |
dc.description.bitstreamurl | http://deepblue.lib.umich.edu/bitstream/2027.42/125087/2/3186637.pdf | |
dc.owningcollname | Dissertations and Theses (Ph.D. and Master's) |
Files in this item
Remediation of Harmful Language
The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.
Accessibility
If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.