This thesis presents two measurements of the top quark pair production cross section at {radical}s = 1:96 TeV using data from the D0 experiment. Both measurements are performed in the dilepton final state and make use of secondary vertex b-tagging.

The author presents the measurement of p{bar p} {yields} Z/{gamma}* {yields} e{sup +}e{sup -} + X inclusive differential cross section as a function of boson rapidity. The data, which correspond to an integrated luminosity of 0.4 fb{sup -1}, were collected with D0 detector at Tevatron p{bar p} collider. At the Run II energy of {radical}s = 1.96 TeV, Z bosons are produced with rapidity out to {+-} 3. The cross section is measured in a mass range between 71 to 111 GeV for the allowed kinematic range.

Quantum Chromodynamics (QCD) is the gauge theory that governs the strong interactions between quarks and gluons inside hadrons like, for example, protons and neutrons. It shows two well established characteristics, related to the non-Abelian nature of the theory, that dominate its phenomenology: asymptotic freedom and color confinement. The dependence of the strong coupling, {alpha}{sub s}(Q{sup 2}), with the hard scale is such that it decreases with decreasing the distance between partons. This allows to perform precise theoretical calculations at large energy transfer (short distances) using perturbative QCD (pQCD). On the other hand, the strength of the interaction increases with the distance between partons and thus colored quarks and gluons are forced to be confined inside colorless hadrons.

Determination of application times-to-solution for large-scale clustered computers continues to be a difficult problem in high-end computing, which will only become more challenging as multi-core consumer machines become more prevalent in the market. Both researchers and consumers of these multi-core systems desire reasonable estimates of how long their programs will take to run (time-to-solution, or TTS), and how many resources will be consumed in the execution. Currently there are few methods of determining these values, and those that do exist are either overly simplistic in their assumptions or require great amounts of effort to parameterize and understand. One previously untried method is queuing network modeling (QNM), which is easy to parameterize and solve, and produces results that typically fall within 10 to 30% of the actual TTS for our test cases. Using characteristics of the computer network (bandwidth, latency) and communication patterns (number of messages, message length, time spent in communication), the QNM model of the NAS-PB CG application was applied to MCR and ALC, supercomputers at LLNL, and the Keck Cluster at USF, with average errors of 2.41%, 3.61%, and -10.73%, respectively, compared to the actual TTS observed. While additional work is necessary to improve the predictive capabilities of …

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In this thesis they report the measurement of ratios of branching fractions: {Beta}(B{sub s}{sup 0} {yields} D{sub s}{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -})/{Beta}(B{sup 0} {yields} D{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -}), and {Beta}(B{sup 0} {yields} D{sup -}D{sub s}{sup +})/{Beta}(B{sup 0} {yields} D{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -}), using 355 pb{sup -1} of data collected by CDF detector at the Tevatron p{bar p} collider at {radical}s = 1.96 TeV.