[en] A first study of single diffractive central high-p_T dijet events in p(bar p) collisions at center-of-mass energy √s = 1.96 TeV is presented, using data recorded by the D0 detector at the Tevatron during RunIIa in 2002-2004. The total integrated luminosity corresponding to the data sample is 398 pb^-1. A diffractive sample is selected using a rapidity gap approach. A precise definition of the rapidity gap constitutes the first part of the thesis. The rapidity gap is defined by means of two parts of the D0 detector--luminosity detectors and calorimeter. Luminosity detectors serve as a basic indicators of diffractive candidates and the calorimeter is used to confirm the low energy activity in the forward region (a rapidity gap). Presented studies of energy deposited in forward part of calorimeter by various types of events yield two rapidity gap definitions. Both of them use a fixed rapidity interval in calorimeter |η| (element_of) [2.6,5.2] and introduce an upper limit on the energy deposited in this region. First definition, which corresponds to the lowest systematical errors, uses a limit of 10 GeV, an energy limit in the second definition is set to 3 GeV. This alternative definition corresponds to the lowest contamination of diffractive sample by non-diffractive events, on the other hand it is accompanied with rejection of high percentage of diffractive candidates. Using the gap definition dijet diffractive data are then selected and compared to inclusive dijet events in various distributions. The main focus is to measure the difference in azimuthal angles between two leading jets in events with at least two high p_t central jets. This variable is sensitive to the dynamics of the process. Indeed, the results show the different behavior of Δφ distributions between the inclusive and diffractive samples. It is also shown that this difference is bigger for lower p_T jets. Other distributions presented in the thesis show that most of the properties are the same for inclusive and diffractive events. The only observed difference is in the transversal properties of the jets, which could be explained as that diffractive jets are narrower than inclusive ones. Results are compared to Monte Carlo Pomwig (for diffractive sample) and Herwig (for inclusive sample); both show a good agreement with the data

[en] The D0 experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to D0

[en] A search for the production of neutral Higgs bosons Φ decaying into τ⁺τ^- final states in p(bar p) collisions at a center-of-mass energy of 1.96 TeV is presented. The data, corresponding to an integrated luminosity of approximately 325 pb^-1, were collected by the D0 experiment at the Fermilab Tevatron Collider. Since no excess compared to the expectation from standard model processes is found, limits on the production cross section times branching ratio are set. The results are combined with those obtained from the D0 search for Φb((bar b)) → b(bar b)b((bar b)) and are interpreted in the minimal supersymmetric standard model

[en] The authors present a search for supersymmetry in the R-parity violating resonant production and decay of smuons and muon-sneutrinos in the channels (tilde μ) → (tilde χ)₁⁰ μ, (tilde μ) → (tilde χ)_2,3,4⁰ μ, and (tilde ν)_μ → (tilde χ)_1,2^± μ. They analyzed 0.38 fb^-1 of integrated luminosity collected between April 2002 and August 2004 with the D0 detector at the Fermilab Tevatron Collider. The observed number of events is in agreement with the standard model expectation, and we calculate 95% C.L. limits on the slepton production cross section times branching fraction to gaugino plus muon, as a function of slepton and gaugino masses. In the framework of minimal supergravity, we set limits on the coupling parameter λ'₂₁₁, extending significantly previous results obtained in Run I of the Tevatron and at the CERN LEP collider

[en] We present a study of events with Z bosons and jets produced at the Fermilab Tevatron Collider in p(bar p) collisions at a center of mass energy of 1.96 TeV. The data sample consists of nearly 14,000 Z/γ* → e⁺e^- candidates corresponding to the integrated luminosity of 340 pb^-1 collected using the D0 detector. Ratios of the Z/γ* + (ge) n jet cross sections to the total inclusive Z/γ* cross section have been measured for n = 1 to 4 jet events. Our measurements are found to be in good agreement with a next-to-leading order QCD calculation and with a tree-level QCD prediction with parton shower simulation and hadronization