This study presents the measurement of the rapidity distributions in events containing a Z boson and a jet in proton-proton collisions at a center-of-mass energy of 7 TeV. The data correspond to an integrated luminosity of approximately 5 fb-11, recorded by the CMS detector at the Large Hadron Collider (LHC). The measured angular distributions are compared with the predictions from next-to-leading order perturbative QCD calculations and two generator programs that combine tree-level matrix element calculations with parton showers. We also present a measurement of jet production rates in association with a Z boson using data recorded at a center-of-mass energy of 8 TeV and with an integrated luminosity of 19.8 fb-1. This measurement provides a stringent test of perturbative QCD calculations, and the result is compared with predictions from theoretical calculations.

"This thesis presents the measurement of the production cross sections of jets in association with a Z boson in proton-proton collisions at √s = 8 TeV with an integrated luminosity of 20.3 fb−1 recorded by the ATLAS experiment at the Large Hadron Collider at CERN. Inclusive and differential Z/[gamma]∗(→ e+e−)+jets cross sections are measured for jets with a transversemomentum pT(jet) > 30 GeV and rapidity |y(jet)| 4.4. Z boson candidates are identified by their decay into electron pairs. In order to stringently probe the modelling of Z/[gamma]∗+jets production by Monte Carlo generators in regions of high-pT phase space typical for Higgs boson decay and searches for new physics, events with high-pT final states are investigated. High-pT final states are defined as events with either pT(Z) 300 GeV or pT(leading jet) > 300 GeV. A set of four observables, sensitive to the topology of the event, are measured for the standard event selection as well as in the regions of high-pT phase space. The results from data are unfolded to particle level and compared to calculations of the matrix element from Monte Carlo generators Alpgen+Pythia and Sherpa interfaced to a parton shower. The results show that Sherpa tends to model Z/[gamma]∗+jets production in high-pT regions of phase space much better than Alpgen+Pythia." --

This thesis presents the measurements of the production cross section of jets in association with a Z boson in pp-collisions at √s = 7 TeV with an integrated luminosity of ∫Ldt = 36-1 and ∫Ldt = 4.6 fb-1 recorded by the ATLAS experiment at the Large Hadron Collider in Geneva. Inclusive and differential Z(→e+e-) + jets cross sections are measured for jets with a transverse momentum pT(jet) > 30 GeV and rapidity |y(jet)|

Measurements of the associated production of a Z boson with at least one jet originating from a b quark in proton-proton collisions at $\sqrt{s}$ = 8 TeV are presented. Differential cross sections are measured with data collected by the CMS experiment corresponding to an integrated luminosity of 19.8 inverse femtobarns. Z bosons are reconstructed through their decays to electrons and muons. Cross sections are measured as a function of observables characterizing the kinematics of the b jet and the Z boson. Ratios of differential cross sections for the associated production with at least one b jet to the associated production with any jet are also presented. The production of a Z boson with two b jets is investigated, and differential cross sections are measured for the dijet system. Results are compared to theoretical predictions, testing two different flavour schemes for the choice of initial-state partons.

Measurements of jet production rates in association with W and Z bosons for jet transverse momenta above 30 GeV are reported, using a sample of proton-proton collision events recorded by CMS at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 36 inverse picobarns. The study includes the measurement of the normalized inclusive rates of jets sigma(V +>= n jets)/sigma(V), where V represents either a W or a Z. In addition, the ratio of W to Z cross sections and the W charge asymmetry as a function of the number of associated jets are measured. A test of Berends--Giele scaling at sqrt(s) = 7 TeV is also presented. The measurements provide a stringent test of perturbative-QCD calculations and are sensitive to the possible presence of new physics. The results are in agreement with the predictions of a simulation that uses explicit matrix element calculations for final states with jets.

The Black Book of Quantum Chromodynamics is an in-depth introduction to the particle physics of current and future experiments at particle accelerators. The book offers the reader an overview of practically all aspects of the strong interaction necessary to understand and appreciate modern particle phenomenology at the energy frontier. It assumes a working knowledge of quantum field theory at the level of introductory textbooks used for advanced undergraduate or in standard postgraduate lectures. The book expands this knowledge with an intuitive understanding of relevant physical concepts, an introduction to modern techniques, and their application to the phenomenology of the strong interaction at the highest energies. Aimed at graduate students and researchers, it also serves as a comprehensive reference for LHC experimenters and theorists. This book offers an exhaustive presentation of the technologies developed and used by practitioners in the field of fixed-order perturbation theory and an overview of results relevant for the ongoing research programme at the LHC. It includes an in-depth description of various analytic resummation techniques, which form the basis for our understanding of the QCD radiation pattern and how strong production processes manifest themselves in data, and a concise discussion of numerical resummation through parton showers, which form the basis of event generators for the simulation of LHC physics, and their matching and merging with fixed-order matrix elements. It also gives a detailed presentation of the physics behind the parton distribution functions, which are a necessary ingredient for every calculation relevant for physics at hadron colliders such as the LHC, and an introduction to non-perturbative aspects of the strong interaction, including inclusive observables such as total and elastic cross sections, and non-trivial effects such as multiple parton interactions and hadronization. The book concludes with a useful overview contextualising data from previous experiments such as the Tevatron and the Run I of the LHC which have shaped our understanding of QCD at hadron colliders.