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The authors measure the time-dependent CP asymmetry parameters in B{sup 0} {yields} K{sup +}K{sup -}K{sup 0} based on a data sample of approximately 277 million B-meson pairs recorded at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II B-meson Factory at SLAC. They reconstruct two-body B{sup 0} decays to {phi}(1020)K{sub s}{sup 0} and {phi}(1020)K{sub L}{sup 0}. Using a time-dependent maximum-likelihood fit, they measure sin2{beta}{sub eff}({phi}K{sup 0}) = 0.48 {+-} 0.28 {+-} 0.10, and C({phi}K{sup 0}) = 0.16 {+-} 0.25 {+-} 0.09, where the first error is statistical, and the second is systematic. They also present measurements of the CP-violating asymmetries in the decay B{sup 0} {yields} f{sub 0}({yields} {pi}{sup +}{pi}{sup -})K{sub s}{sup 0}. The results are obtained from a data sample of 209 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays, also collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. From a time-dependent maximum-likelihood fit they measure the mixing-induced CP violation parameter S(f{sub 0}(980)K{sub S}{sup 0}) = - sin 2{beta}{sub eff}f{sub 0}(980)K{sub S}{sup 0} = -0.95{sub -0.23}{sup +0.32} {+-} 0.10 and the direct CP violation parameter C(f{sub 0}(980)K{sub S}{sup 0}) = - 0.24 {+-} 0.31 {+-} 0.15, where the first errors are statistical and …

This thesis is focused on an inclusive search of the t{bar t} {yields} E{sub T} + jets decay channel by means of neural network tools in proton antiproton collisions at {radical}s = 1.96 TeV recorded by the Collider Detector at Fermilab (CDF). At the Tevatron p{bar p} collider top quarks are mainly produced in pairs through quark-antiquark annihilation and gluon-gluon fusion processes; in the Standard Model description, the top quark then decays to a W boson and a b quark almost 100% of the times, so that its decay signatures are classified according to the W decay modes. When only one W decays leptonically, the t{bar t} event typically contains a charged lepton, missing transverse energy due to the presence of a neutrino escaping from the detector, and four high transverse momentum jets, two of which originate from b quarks. In this thesis we describe a t{bar t} production cross section measurement which uses data collected by a 'multijet' trigger, and selects this kind of top decays by requiring a high-P{sub T} neutrino signature and by using an optimized neural network to discriminate top quark pair production from backgrounds. In Chapter 1, a brief review of the Standard Model of …

The MINOS experiment is designed to study neutrino oscillations. It uses an accelerator generated beam of neutrinos and two detectors, the smaller at a distance of 1km and the larger at 735 km. By comparing the spectrum and flavour composition of the beam at the two detectors precise determinations of the oscillation parameters are possible. This thesis concentrates on the analysis of data from the larger Far Detector. By studying the spectrum of neutral current events it is possible to look for evidence of non-interacting 'sterile' neutrinos. The thesis describes how events are selected for this analysis, and a method for discriminating between charged current and neutral current events. The systematic uncertainties resulting from these cuts are evaluated. Several techniques for using Near Detector data to eliminate systematic uncertainties in the predicted Far Detector spectrum are compared. An oscillation analysis, based on the first year of MINOS data, uses the selected events to make a measurement of f{sub s}, the fraction of unseen neutrinos that are sterile. The measured value is f{sub s} = 0.07{sup +0.32} at 68%C.L., and is consistent with the standard three-neutrino picture, which has no sterile neutrino.

In the first part of this work, we present a search for WW and WZ production in charged lepton, neutrino plus jets final states produced in p{bar p} collisions with {radical}s = 1.96 TeV at the Fermilab Tevatron, using 1.2 fb{sup -1} of data accumulated with the CDF II detector. This channel is yet to be observed in hadron colliders due to the large singleWplus jets background. However, this decay mode has a much larger branching fraction than the cleaner fully leptonic mode making it more sensitive to anomalous triple gauge couplings that manifest themselves at higher transverse W momentum. Because the final state is topologically similar to associated production of a Higgs boson with a W, the techniques developed in this analysis are also applicable in that search. An Artificial Neural Network has been used for the event selection optimization. The theoretical prediction for the cross section is {sigma}{sub WW/WZ}{sup theory} x Br(W {yields} {ell}{nu}; W/Z {yields} jj) = 2.09 {+-} 0.14 pb. They measured N{sub Signal} = 410 {+-} 212(stat) {+-} 102(sys) signal events that correspond to a cross section {sigma}{sub WW/WZ} x Br(W {yields} {ell}{nu}; W/Z {yields} jj) = 1.47 {+-} 0.77(stat) {+-} 0.38(sys) pb. The 95% …

The study of the top quark pair production mechanism in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV is described. The main subjects are the measurements of the top quark pair production cross section, the top quark mass and a search for a new particle decaying to the top quark pair. The analyses are based on 1.9 fb{sup -1} of data collected by the Collider Detector at Fermilab (CDF) Run II experiment between March 2002 and May 2007, using the lepton+jets events. The measured top quark pair production cross section is 8.2 {+-} 0.5 (stat.) {+-} 0.8 (syst.) {+-} 0.5 (lum.) pb, which is slightly higher than the standard model prediction at the top mass of 175 GeV/c{sup 2}. The top quark mass is an important parameter in the standard model, and also in the experimental studies. The measured top quark mass if 171.6 {+-} 2.0 (stat.) {+-} 1.3(syst.) GeV/c{sup 2}. Finally, they report on a search for a new gauge boson decaying to t{bar t}, which interferes with the standard model gluon in the q{bar q} {yields} t{bar t} production process. They call such a hypothetical particle a 'Massive Gluon'. The observed t{bar t} invariant mass distribution is …

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