A measurement of W boson-photon and Z boson-photon cross sections in the muon channel in 1.8 TeV proton-antiproton collisions
Luchini, Christopher B.
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https://hdl.handle.net/2142/22948
Description
Title
A measurement of W boson-photon and Z boson-photon cross sections in the muon channel in 1.8 TeV proton-antiproton collisions
Author(s)
Luchini, Christopher B.
Issue Date
1994
Doctoral Committee Chair(s)
Errede, Steven M.
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Elementary Particles and High Energy
Language
eng
Abstract
We have measured the production cross sections x decay branching ratios for W + $\gamma$ and Z + $\gamma$ in the muon channel in $\sqrt{s}$ = 1.8 TeV p-p collisions, from 3.54 $\pm$ 0.24 $pb\sp{-1}$ of muon W and Z data from the CDF 1988-89 Tevatron collider run. For photons in the central region ($\vert\eta\vert $ 5.0 GeV and lepton-photon angular separation $\Delta R\sb{\ell\sb\gamma} >$ 0.7, 5 $W\sb{\gamma}$ candidates and 2 $Z\sb{\gamma}$ candidates were observed. From these events, the $\sigma \cdot BR(W + \gamma)$ and $\sigma \cdot BR(Z + \gamma)$ cross sections for the muon samples are measured, and compared with Standard Model predictions. We also determined the cross section ratios, $W\sb{\gamma}$/W, $Z\sb{\gamma}$/Z and $W\sb{\gamma}/Z\sb{\gamma}$, which, along with the previous CDF measurement(s) of the W/Z cross section ratio provide new insight on the Standard Model, and are sensitive to anomalous couplings of the W and Z bosons. Using the $W\sb{\gamma}$ and $Z\sb{\gamma}$ absolute cross section measurements, the absence of an excess of hard photons accompanying W and Z boson production enables us to obtain direct limites on anomalous $WW\sb{\gamma}$, $ZZ\sb{\gamma}$ and $Z\sb{\gamma\gamma}$ couplings. For saturation of unitarity, these experimental limits impose constraints on possible internal (composite) structure for the W and Z bosons with compositeness scale sensitivity up to $\Lambda\sb{W} \sim$ 1 TeV and $\Lambda\sb{Z} \sim$ 250-500 GeV, respectively. These compositeness scale limits probe the possible internal structure of the W to ${\sim}<$2 $\times$ 10$\sp{-4}$fm and internal structure of the Z to ${\sim}<$4-7 $\times$ 10$\sp{-4}$ fm. Limits on the anomalous $W\sb{\gamma}$ and $Z\sb{\gamma}$ couplings also impose constraints on the higher order static and transition EM moments of the W and Z boson, respectively. The muon channel measurements were combined with those made from the electron channel to arrive at $\mu$ + e combined $\sigma \cdot$ BR(W) + $\gamma$) and $\sigma \cdot$ BR(Z + $\gamma$) absolute cross sections, and limits on the anomalous couplings for combined $\mu$ + e $W\sb{\gamma}$ and $Z\sb{\gamma}$.
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