Measurement of $Z/\gamma^*$ + Jets Differential Cross Sections with the CDF Detector at $\sqrt{s} = 1.96$ TeV

Abstract

Experimental and theoretical effort of understanding the Z/gamma* + jets final state has a double reason, on one hand the motivation is to test the ability of the Standard Model theory of particle physics to make accurate predictions when electroweak and QCD physics are involved at different scales, ranging from the non perturbative evolution of hadrons to perturbative QCD and electroweak calculations at a scale mu >~ M(Z). On the other hand a precise modeling of Z/gamma* + jets processes is a fundamental prerequisite in the search for new physics in final states with jets and leptons or missing transverse energy. In addition the Z/gamma* -> l+l- + jet final state is appropriate to calibrate jet reconstruction and reduce the experimental uncertainties related to the jet energy scale. In response to a widespread interest in jets production associated to vector bosons, many of the recently developed perturbative QCD calculations and Monte Carlo tools include Z/gamma* and W + jets production at hadron colliders. The approximately 10 fb-1 of integrated luminosity collected with the CDF detector in Tevatron Run II allows for precise measurement of inclusive and differential cross sections of Z/gamma* + jets production, and opens the possibility of testing the accuracy of state of the art theoretical predictions. The results presented in this thesis provides an experimental feedback to the recent development in theoretical calculations and validate the new predictions through a comparison with the measured cross sections. The comparison includes a careful study of the uncertainties associated to the theoretical models, and sensible variations of parameters and settings of the predictions.