Author: Silke Duensing

Publisher:

Published: 2004

Total Pages: 129

ISBN-13:

In this thesis the first measurement of {sigma}(p{bar p}) {yields} Z{sup 0} {yields} {tau}{bar {tau}} with the D0 detector at the Tevatron is presented. The tau pair candidates are recorded by the D0 detector using p{bar p} interactions at a center-of-mass energy of 1.96 TeV. Events in which one tau decays into a muon and the other tau final state is hadronic with one charged particle are selected for this analysis. The selection criteria for the hadronic tau decay are based on the tau final state, hence for two channels of one-prong taus: single charged pion ({tau}{sub {pi}}) and rho decays ({tau}{sub {rho}}). The selection is based on simple cuts on a number of discriminating variables and the cut values have been optimized for the best cross section measurement. Of hadronic tau candidates that have been reconstructed as {tau}{sub {pi}} candidates, 0.801 {+-} 0.017 {+-} 0.066 pass the selection cut; in the case of {tau}{sub {rho}} taus, the selection efficiency is 0.676 {+-} 0.009 {+-} 0.009. Of all QCD jets that are reconstructed as hadronic tau candidates, 0.0093 {+-} 0.0002 pass the {tau}{sub {pi}} selection cuts and 0.0122 {+-} 0.0002 the {tau}{sub {rho}} cuts. The cross section has been measured to be 274 {+-} 121 {+-} 40 {+-} 27 pb in the {mu}{tau}{sub {pi}} channel and 273 {+-} 40{sub -23}{sup +18} {+-} 27 pb in the {mu}{tau}{sub {rho}} channel, resulting in a combined measurement of {sigma}(p{bar p} {yields} Z{sup 0} {yields} {tau}{bar {tau}}) = 273 {+-} 38{sub -23}{sup +19} {+-} 27 pb which agrees with the SM prediction within errors. The errors are dominated by the statistical error as only the first data taken with the D0 detector in Run II was used. Due to the small set of tau candidates, the calorimeter energy scale could not yet be determined using data and this uncertainty is the largest systematic effect on the measurement. Another large contribution arises from the uncertainty of 10% on the luminosity measurement. This is expected to decrease significantly in the future. It was demonstrated that the currently available tools are sufficient to use tau leptons in the measurement of a SM process. This opens the door to the use of hadronic tau decays in the search for new particles, like SUSY particles, that decay preferentially to tau leptons in a number of models or the Higgs boson of either the SM or extended model. Doing physics at the Tevatron as the accelerator at the current energy frontier is our current best hope to find the yet elusive Higgs boson and will allow to either find proof of physics beyond the Standard Model or tighten the constraints on these models.