Measurement of the t$\bar{t}$, WW and Z → ττ Production Cross Sections in p$\bar{p}$ collisions at √s = 1.96 TeV

Abstract

In this thesis we present a new technique to analyze events containing two highly energetic leptons, as a probe of the Standard Model. The philosophy is to consider the data in a more global way, as opposed to the more traditional process dependent approach of extracting a given signal over the expected backgrounds by using various kinematical requirements. We use our global technique to simultaneously measure the cross sections of the main Standard Model processes; the tt, W W and Z → τ τ production from pp collisions at √ s =1.96 TeV in the CDF detector at Fermilab.We select events by requiring they contain two highly energetic leptons (eµ, ee, or µµ), and make no other kinematic requirements, except for the ee and µµ channels.We then use a likelihood fit of the data in the two-dimensional phase space defined by the missing transverse energy ( E T ) and the number of jets in the event (N jet ), to the expected Standard Model distributions, to simultaneously extract the production cross-sections of the main process contributing to our dilepton sample. Our results, using about 360 pb −1 of data, are:where the first error comes from the likelihood fit and includes the statistical error, all acceptance systematic errors, and the uncertainty in the integrated luminosity, and the second error is from systematic uncertainties associated with the modelling of the E T -N jet distribution. By requiring a minimum of selection criteria we are optimally using the statistical power of the data for given lepton definitions. We used this global method to successfully extract cross-section measurements.iv .