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Using data from the fixed target charm-photoproduction experiment, Fermilab FOCUS/E831, they studied the asymmetric production of the mesons: D{sup 0}, D{sup +} y D{sub s}{sup +}. Even when the asymmetry in the production of charm particles, defined as the ratio between particles and antiparticles, at next leading order in quantum chromodynamics (QCD) is almost zero, in data we observe asymmetries probably associate dto the fragmentation processes. Since these are the less understood phenomena in QCD, the results in the present work could be of great importance to understand them. We found asymmetries in the production of the mesons D{sup +} and D{sup 0} (statistic significant), for the D{sub s}{sup +} we only observed an asymmetry not conclusive. We also report a study of the production asymmetries vs. the kinematic variables: p{sub T}{sup 2} (square transversal momentum of the particles), p{sub L} or p{sub Z} (longitudinal momentum), x{sub F} (Feynman x) and E{sub {gamma}} (photon beam energy).

This thesis is dedicated to the study of the first data taken by the D0 detector during the Run II of the Tevatron. Supersymmetric particles have been search for in proton-antiproton collisions, with a center of mass energy of 1.96 TeV. In the framework of supersymmetry with R-parity violation, I have studied the pair production of Gauginos, leading to a pair of LSP ({chi}{sub 1}{sup 0}), each one decaying into ee{nu}{sub {mu}} or e{mu}{nu}{sub e} with a {lambda}{sub 121} coupling. The final state contains at least two electrons: I have thus paid special attention in this work to the methods concerning identification and mis-identification of electromagnetic particles, as well as reconstruction, triggering, and correction (of the reconstructed energy). In a selection of trileptons, with at least two electrons, and some transverse missing energy, we observed 0 event in the 350 pb{sup -1} of analyzed data, for 0,4{sub -0,05}{sup +0,35}(stat) {+-} 0,16 (sys) expected from the Standard Model contributions. In the signal considered in this analysis, the selection efficiency is around 12%. Results have been studied in two models: mSUGRA and MSSM. In mSUGRA model, limits on m{sub 1/2} and lightest gauginos's masses have been obtained, with tan{beta} = 5, A{sub …