This thesis describes a first measurement of the W Boson mass through the decay into a muon and a neutrino in Run 2 of the Tevatron. The W Bosons are produced in proton-antiproton collisions at a center of mass energy of 1.96 TeV. The data sample used for this analysis corresponds to 200 pb{sup -1} recorded by the upgraded Collider Detector at Fermilab. The most important quantity in this measurement is the momentum of the muon measured in a magnetic spectrometer which is calibrated using the two quarkonium resonances J/{Psi} and {Upsilon}(1S). Systematic uncertainties arise from the modeling of the recoil when the W Boson is produced, the momentum calibration, the modeling of W Boson production and decay dynamics and backgrounds. The result is: M{sub W} = 80408 {+-} 50(stat.) {+-} 57(syst.) MeV/c{sup 2}.

The measurement of the top-antitop pair production cross section in p{bar p} collisions at {radical}s = 1.96 TeV in the dielectron decay channel using 384 pb{sup -1} of D0 data yields a t{bar t} production cross-section of {sigma}{sub t{bar t}} = 7.9{sub -3.8}{sup +5.2}(stat){sub -1.0}{sup +1.3}(syst) {+-} 0.5 (lumi) pb. This measurement [98] is based on 5 observed events with a prediction of 1.04 background events. The cross-section corresponds to the top mass of 175 GeV, and is in good agreement with the Standard Model expectation of 6.77 {+-} 0.42 pb based on next-to-next-leading-order (NNLO) perturbative QCD calculations [78]. This analysis shows significant improvement from our previous cross-section measurement in this channel [93] with 230 pb{sup -1} dataset in terms of significantly better signal to background ratio and uncertainties on the measured cross-section. Combination of all the dilepton final states [98] yields a yields a t{bar t} cross-section of {sigma}{sub t{bar t}} = 8.6{sub -2.0}{sup +2.3}(stat){sub -1.0}{sup +1.2}(syst) {+-} 0.6(lumi) pb, which again is in good agreement with theoretical predictions and with measurements in other final states. Hence, these results show no discernible deviation from the Standard Model. Fig. 6.1 shows the summary of cross-section measurements in different final states …

This dissertation reports the results of a search for charged Higgs bosons in the decays of t{bar t} pairs produced in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. The search is performed on a data sample recorded by the upgraded Collider Detector at Fermilab and corresponding to an integrated luminosity of 193 pb{sup -1}. The search is based on the relative rates of events in the different t{bar t} decay channels. Results are obtained in the context of different models. In the context of the minimal supersymmetric extension of the Standard Model (MSSM), for which they fully account for radiative and Yukawa coupling corrections, regions in the (m{sub H{sup {+-}}}, tan ({beta})) plane are excluded. In the Tauonic Higgs Model in which the charged Higgs is assumed to decay exclusively to {bar {tau}}, the BR(t {yields} H{sup +}b) is constrained to be less than 0.4 at 95% C.L. If no assumption is made on the charged Higgs decay, the BR(t {yields} H{sup +}b) is constrained to be less than 0.90 at 95% C.L. No evidence for charged Higgs production is found.

In May 2000, the Cerro Grande Fire burned approximately 17,200 ha in north-central New Mexico as the result of an escaped prescribed burn initiated by Bandelier National Monument. The interaction of large-scale fires, vegetation, and elk is an important management issue, but few studies have addressed the ecological implications of vegetative succession and landscape heterogeneity on ungulate populations following large-scale disturbance events. Primary objectives of this research were to identify elk movement pathways on local and landscape scales, to determine environmental factors that influence elk movement, and to evaluate movement and distribution patterns in relation to spatial and temporal aspects of the Cerro Grande Fire. Data collection and assimilation reflect the collaborative efforts of National Park Service, U.S. Forest Service, and Department of Energy (Los Alamos National Laboratory) personnel. Geographic positioning system (GPS) collars were used to track 54 elk over a period of 3+ years and locational data were incorporated into a multi-layered geographic information system (GIS) for analysis. Preliminary tests of GPS collar accuracy indicated a strong effect of 2D fixes on position acquisition rates (PARs) depending on time of day and season of year. Slope, aspect, elevation, and land cover type affected dilution of precision (DOP) values …