Doctor of Philosophy / Department of Physics / Yurii Maravin / This dissertation describes a comprehensive study of the Zgamma [to] eegamma/mumugamma/nu[bar]nugamma
process. The data have been collected with the D0 detector at the Fermilab Tevatron p[bar]p collider with
the center-of-mass energy of 1.96 TeV, and correspond to up to 3.6 fb[superscript]-1 of integrated luminosity.
Firstly, in this study we perform a measurement of the Zgamma production cross section.
The measured cross sections in both llgamma (l = e or mu) and nu[bar]nugamma
channels are the most precise cross sections measured at hadron colliders to date, and they agree within
uncertainties with the theoretical calculations to the next-to-leading order. We claim the first
observation of the Zgamma [to] nu[bar]nugamma process at hadron colliders at 5.1 standard deviations
statistical significance.
We also conduct a search for anomalous Zgamma processes. Such anomalous Zgamma processes, where a
Z boson couples to a photon, result in an increased cross section and an enhancement of the production of
high-energetic photons. Thus, an observation of this kind might possibly indicate the presence of
new physics. Having found no excess of data over the SM expectations, we set the most restrictive
95% C.L. limits on the anomalous trilinear Zgammagamma and ZZgamma gauge couplings (ATGC) at hadron
colliders to date: |h[subscript]30[superscript]gamma| < 0.033, |h[subscript]40[superscript]gamma| < 0.0017,
|h[subscript]30[superscript]Z| < 0.033, and |h[subscript]40[superscript]Z| < 0.0017, which mark almost three
times improvement over the most recent results published to date. Three out of four current limits improve on the
LEP limits, and are the tightest limits on ATGC in the world.
Finally, we performed a search for narrow vector and scalar resonances that decay to Zgamma. Many
extensions of the SM predict such resonances, thus making this search a test of the gauge sector of
the SM. We found no significant deviation of data from the SM predictions, and hence we set 95% C.L
upper limits on the production cross section of the resonances.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/1347 |
| Date | January 1900 |
| Creators | Ferapontov, Alexey V. |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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