Measurement of the W and Z Cross Sections in the Electron Channel for p¯p Collisions at √s = 1.96 TeV and Extraction of the W Total Width from the Ratio

Abstract

Term Degree Awarded: Fall 2005 University of KansasThis dissertation presents measurements of the inclusive production cross sections for W and Z gauge bosons decaying through the electron channel with pp collisions at a center-of-mass energy of 1.96 TeV. The ratio of these cross sections is then used to extract the W total width.The Standard Model (SM) of electroweak and strong interactions is a collection of theories which together encompass what is currently known about the elementary particles that make up matter and the forces through which they interact. Experimentalists are constantly searching for violations of the Standard Model by making precision measurements of predicted interactions. The decay of the W boson is one such interaction. The rate of its decay is reflected in its width which is predicted to high precision using Standard Model-based calculations. Therefore, a high precision experimental width measurement would be very sensitive to any such violation. In principle the W and Z boson production cross sections could also be good Standard Model tests. However, a precise knowledge of integrated luminosity is required which is unfortunately difficult to obtain at the Tevatron. In fact, the W and Z cross section results can be used to obtain a more precise luminosity measurement.The data set consists of a total integrated luminosity of 177 pb Sources of uncertainty arise from limited statistics (stat), systematic effects (sys), parton distribution function parameters (pdf) and integrated luminosity (lumi). Indirect measurements of the branching ratio, Br(W → e ± ν), and the W total width, Γ W , are extracted from the ratio, R:

An indirect measurement of the width of the w boson at the D0 experiment

“…Using an integrated luminosity of 177 pb −1 , the width of the W Boson was found to be Γ W =2.080 +0.054/-0.052 GeV [71].…”

Measurement of z boson transverse momentum in proton - anti-proton collisions at √s = 1.96 TeV

“…The methods of measuring the position resolutions from a data sample of electrons passing the preselection requirements are described in [55]. The idea of the method is to treat the track position as the true position of the electron, and measure the difference between the track position and the calorimeter position to extract the resolutions.…”