This dissertation presents the first search for the standard model Higgs boson (H) in decay topologies containing a muon, an imbalance in transverse momentum (E{sub T}) and jets, using p{bar p} collisions at {radical}s = 1.96 TeV with an integrated luminosity of 4.3 fb{sup -1} recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primary to contributions from Higgs bosons produced through gluon fusion, with subsequent decay H {yields} WW {yields} {mu}{nu}jj where W represents a real or virtual W boson. In the absence of signal, limits are set at 95% confidence on the production and decay of the standard model Higgs boson for M{sub H} in the range of 115-200 GeV. For M{sub H} = 165 GeV, the observed and expected limits are factors of 11.2 larger than the standard model value. Combining this channel with e{nu}jj final states and including earlier data to increase the integrated luminosity to 5.4 fb{sup -1} produces observed(expected) limits of 5.5(3.8) times the standard model value.

The Standard Model of particle physics provides an excellent description of particle interactions at energies up to {approx}1 TeV, but it is expected to fail above that scale. Multiple models developed to describe phenomena above the TeV scale predict the existence of very massive, vector-like quarks. A search for single electroweak production of such particles in p{anti p} collisions at a center-of-mass energy of 1.96 TeV is performed in the W+jets and Z+jets channels. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb{sup -1}. Events consistent with a heavy object decaying to a vector boson and a jet are selected. We observe no significant excess in comparison to the background prediction and set 95% confidence level upper limits on production cross sections for vector-like quarks decaying to W+jet and Z+jet. Assuming a vector-like quark -- standard model quark coupling parameter {tilde {kappa}}{sub qQ} of unity, we exclude vector-like quarks with mass below 693 GeV for decays to W+jet and mass below 449 GeV for decays to Z+jet. These represent the most sensitive limits to date.

The MINOS experiment is a long-baseline neutrino oscillation experiment in the the NuMI beamline at Fermilab, USA. Using a near detector at 1 km distance from the neutrino production target, and a far detector at 735 km from the target, it is designed primarily to measure the disappearance of muon neutrinos. This thesis presents an analysis using MINOS data of the possibility of oscil- lation of the neutrinos in the NuMI beam to a hypothetical sterile flavour, which would have no Standard Model couplings. Such oscillations would result in a deficit in the neutral current interaction rate in the MINOS far detector relative to the expectation derived from the near detector data. The method used to identify neutral current and charged current events in the MINOS detectors is described and a new method of predicting and fitting the far detector spectrum presented, along with the effects of systematic uncertainties on the sterile neutrino oscillation analysis. Using this analysis, the fraction f{sub s} of the disappearing neutrinos that go to steriles is constrained to be below 0.15 at the 90% confidence level in the absence of electron neutrino appearance in the NuMI beam. With electron appearance at the CHOOZ limit, f{sub …

The COUPP collaboration has successfully used bubble chambers, a technology previously applied only to high-energy physics experiments, as direct dark matter detectors. It has produced the world's most stringent spin-dependent WIMP limits, and increasingly competitive spin-independent limits. These limits were achieved by capitalizing on an intrinsic rejection of the gamma background that all other direct detection experiments must address through high-density shielding and empirically-determined data cuts. The history of COUPP, including its earliest prototypes and latest results, is briefly discussed in this thesis. The feasibility of a new, windowless bubble chamber concept simpler and more inexpensive in design is discussed here as well. The dark matter limits achieved with a 15 kg windowless chamber, larger than any previous COUPP chamber (2 kg, 4 kg), are presented. Evidence of the greater radiopurity of synthetic quartz compared to natural is presented using the data from this 15 kg device, the first chamber to be made from synthetic quartz. The effective reconstruction of the three-dimensional positions of bubbles in a highly distorted optical field, with ninety-degree bottom lighting similar to cloud chamber lighting, is demonstrated. Another innovation described in this thesis is the use of the sound produced by bubbles recorded by an …

We present a search for associated production of Z and Higgs bosons in 4.2 fb{sup -1} of {bar p}p collisions at {radical}s = 1.96 TeV, produced in RunII of the Tevatron and recorded by the D0 detector. The search is performed in events containing at least two muons and at least two jets. The ZH signal is distinguished from the expected backgrounds by means of multivariate classifiers known as random forests. Binned random forest output distributions are used in comparing the data to background-only and signal+background hypotheses. No excess is observed in the data, so we set upper limits on ZH production with a 95% confidence level.

The production of single, highly forward {pi}{sup 0} mesons by NC coherent neutrino-nucleus interactions ({nu}{sub {mu}} + N {yields} {nu}{sub {mu}} + N + {pi}{sup 0}) is a process which probes fundamental aspects of the weak interaction. This reaction may also pose as a limiting background for long baseline searches for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations if the neutrino mixing angle {theta}{sub 13} is very small. The high-statistics sample of neutrino interactions recorded by the MINOS Near Detector provides an opportunity to measure the cross section of this coherent reaction on a relatively large-A nucleus at an average E{sub {nu}} = 4.9 GeV. A major challenge for this measurement is the isolation of forward-going electromagnetic (EM) showers produced by the relatively rare coherent NC({pi}{sup 0}) process amidst an abundant rate of incoherently produced EM showers. The backgrounds arise from single {pi}{sup 0} dominated NC events and also from quasi-elastic-like CC scattering of electron neutrinos. In this Thesis the theory of coherent interactions is summarized, and previous measurements of the coherent NC({pi}{sup 0}) cross section are reviewed. Then, methods for selecting a sample of coherent NC({pi}{sup 0}) like events, extracting the coherent NC({pi}{sup 0}) event rate from that sample, estimating …

The MiniBooNE experiment was designed to perform a search for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations in a region of {Delta}m{sup 2} and sin{sup 2} 2{theta} very different from that allowed by standard, three-neutrino oscillations, as determined by solar and atmospheric neutrino experiments. This search was motivated by the LSND experimental observation of an excess of {bar {nu}}{sub e} events in a {bar {nu}}{sub {mu}} beam which was found compatible with two-neutrino oscillations at {Delta}m{sup 2} {approx} 1 eV{sup 2} and sin{sup 2} 2{theta} < 1%. If confirmed, such oscillation signature could be attributed to the existence of a light, mostly-sterile neutrino, containing small admixtures of weak neutrino eigenstates. In addition to a search for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations, MiniBooNE has also performed a search for {bar {nu}}{sub {mu}} {yields} {bar {nu}}{sub e} oscillations, which provides a test of the LSND two-neutrino oscillation interpretation that is independent of CP or CPT violation assumptions. This dissertation presents the MiniBooNE {nu}{sub {mu}} {yields} {nu}{sub e} and {bar {nu}}{sub {mu}} {yields} {bar {nu}}{sub e} analyses and results, with emphasis on the latter. While the neutrino search excludes the two-neutrino oscillation interpretation of LSND at 98% C.L., the antineutrino search shows an …

Elucidating the nature of neutrino oscillation continues to be a goal in the vanguard of the efforts of physics experiment. As neutrino oscillation searches seek an increasingly elusive signal, a thorough understanding of the possible backgrounds becomes ever more important. Measurements of neutrino-nucleus interaction cross sections are key to this understanding. Searches for {nu}{sub {mu}} {yields} {nu}{sub e} oscillation - a channel that may yield insight into the vanishingly small mixing parameter {theta}{sub 13}, CP violation, and the neutrino mass hierarchy - are particularly susceptible to contamination from neutral current single {pi}{sup 0} (NC 1{pi}{sup 0}) production. Unfortunately, the available data concerning NC 1{pi}{sup 0} production are limited in scope and statistics. Without satisfactory constraints, theoretical models of NC 1{pi}{sup 0} production yield substantially differing predictions in the critical E{sub {nu}} {approx} 1 GeV regime. Additional investigation of this interaction can ameliorate the current deficiencies. The Mini Booster Neutrino Experiment (MiniBooNE) is a short-baseline neutrino oscillation search operating at the Fermi National Accelerator Laboratory (Fermilab). While the oscillation search is the principal charge of the MiniBooNE collaboration, the extensive data ({approx} 10{sup 6} neutrino events) offer a rich resource with which to conduct neutrino cross section measurements. This work concerns …

A search for dijet resonance production in a four-jet all-hadronic final state from the D0 detector at Fermilab's Tevatron is presented. The data set, acquired at a p{bar p} center-of-mass energy of {radical}s = 1.96 TeV, contains primarily multijet events and represents approximately 1 fb{sup -1} of data. The cross section limits for associated Higgs production and Technicolor processes are determined through a background subtraction method using data to estimate the background. This four-jet channel is potentially very powerful, but is extremely challenging due to the large multijet background from QCD processes. Background rejection is performed by utilizing b-tagging, pre-selection cuts, a multi-variate boosted decision tree discriminant, and the correlated information contained in the M(bb) and M(jj) dijet invariant masses. The search for V H (WH+ZH) processes yields a 95% confidence level observed upper limit of 20.4 pb on the VH cross section for a Higgs mass of 115 GeV/c{sup 2}. Additionally, a 95% confidence level observed upper limit of 16.7 pb was set for a Higgs boson mass of 125 GeV/c{sup 2} and 24.6 pb was set for a Higgs boson mass of 135 GeV/c{sup 2}. The same data set was used to place limits on the Technicolor process …

The experiment E06010 measured the target single spin asymmetry (SSA) in the semiinclusive deep inelastic (SIDIS) n{up_arrow}(e, e'{pi}{sup -})X reaction with a transversely polarized {sup 3}He target as an e#11;ective neutron target. This is the very #12;rst independent measurement of the neutron SSA, following the measurements at HERMES and COMPASS on the proton and the deuteron. The experiment acquired data in Hall A at Je#11;erson Laboratory with a continuous electron beam of energy 5.9 GeV, probing the valence quark region, with x = 0.13 {rt_arrow} 0.41, at Q{sup 2} = 1.31 {rt_arrow} 3.1 GeV{sup 2}. The two contributing mechanisms to the measured asymmetry, viz, the Collins effect and the Sivers effect can be realized through the variation of the asymmetry as a function of the Collins and Sivers angles. The neutron Collins and Sivers moments, associated with the azimuthal angular modulations, are extracted from the measured asymmetry for the very #12;first time and are presented in this thesis. The kinematics of this experiment is comparable to the HERMES proton measurement. However, the COMPASS measurements on deuteron and proton are in the low-x region. The results of this experiment are crucial as the first step toward the extraction of quark transversity …

We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ({tilde t}{sub 1}) in 5.4 {+-} 0.3 fb{sup -1} of data from the D0 detector at a p{bar p} center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The scalar top quarks are assumed to decay into a b quark, a charged lepton and a scalar neutrino ({tilde {nu}}), and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected and new exclusion limits at the 95% C.L. are set for a portion of the (m{sub {tilde t}{sub 1}}, m{sub {tilde {nu}}}) mass plane.

Knowledge of the electric and magnetic elastic form factors of the nucleon is essential for an understanding of nucleon structure. Of the form factors, the electric form factor of the neutron has been measured over the smallest range in Q{sup 2} and with the lowest precision. Jefferson Lab experiment 02-013 used a novel new polarized {sup 3}He target to nearly double the range of momentum transfer in which the neutron form factor has been studied and to measure it with much higher precision. Polarized electrons were scattered off this target, and both the scattered electron and neutron were detected. G{sup n}{sub E} was measured to be 0.0242 ± 0.0020(stat) ± 0.0061(sys) and 0.0247 ± 0.0029(stat) ± 0.0031(sys) at Q{sup 2} = 1.7 and 2.5 GeV{sup 2}, respectively.

The CP violating phase {beta}{sub s}{sup J/{psi}{phi}} is measured in decays of B{sub s}{sup 0} {yields} J/{psi}{phi}. This measurement uses 5.2 fb{sup -1} of data collected in {radical}s = 1.96 TeV p{bar p} collisions at the Fermilab Tevatron with the CDF Run-II detector. CP violation in the B{sub s}{sup 0}-{bar B}{sub s}{sup 0} system is predicted to be very small in the Standard Model. However, several theories beyond the Standard Model allow enhancements to this quantity by heavier, New Physics particles entering second order weak mixing box diagrams. Previous measurements have hinted at a deviation from the Standard Model expectation value for {beta}{sub s}{sup J/{psi}{phi}} with a significance of approximately 2{sigma}. The measurement described in this thesis uses the highest statistics sample available to date in the B{sub s}{sup 0} {yields} J/{psi}{phi} decay channel, where J/{psi} {yields} {mu}{sup +}{mu}{sup -} and {phi} {yields} K{sup +}K{sup -}. Furthermore, it contains several improvements over previous analyses, such as enhanced signal selection, fully calibrated particle ID and flavour tagging, and the inclusion of an additional decay component in the likelihood function. The added decay component considers S-wave states of KK pairs in the B{sub s}{sup 0} {yields} J/{psi} K{sup +}K{sup -} channel. The …

In the Standard Model of particle physics, the Higgs boson generates elementary particle masses. Current theoretical and experimental constraints lead to a Higgs boson mass between 114.4 and 158 GeV with 95% confidence level. Moreover, Tevatron has recently excluded the mass ranges between 100 and 109 GeV, 158 and 175 GeV with 95% confidence level. These results gives a clear indication to search for a Higgs boson at low mass. The D0 detector is located near Chicago, at the Tevatron, a proton-antiproton collider with an energy in the center of mass of 1.96 TeV. The topic of this thesis is the search for a Higgs boson in association with a Z boson. This channel is sensitive to low mass Higgs boson (<135 GeV) which has a branching ratio H {yields} bb varies between 50% and 90% in this mass range. The decay channel ZH {yields} {nu}{bar {nu}}b{bar b} studied has in the final state 2 heavy-flavor jets and some missing transverse energy due to escaping neutrinos. The heavy-flavor jets identification ('b-tagging') is done with a new algorithm (SLTNN) developped specifically for semi-leptonic decay of b quarks. The Higgs boson search analysis was performed with 3 fb{sup -1} of data. The …

This dissertation presents the results of a search for supersymmetry in proton-antiproton collisions with a center of mass energy of 1.96 TeV studied with the Collider Detector at Fermilab. Our strategy is to select collisions with two photons in the final state that have the properties of being the decays of very massive supersymmetric particles. This includes looking for large total energy from the decayed particles as well as for the presence of particles that leave the detector without interacting. We find no events using 2.6 fb{sup -1} of data collected during the 2004-2008 collider run of the Fermilab Tevatron which is consistent with the background estimate of 1.4 {+-} 0.4 events. Since there is no evidence of new particles we set cross section limits in a gauge-mediated supersymmetry model with {tilde {chi}}{sub 1}{sup 0} {yields} {gamma}{tilde G}, where the {tilde {chi}}{sub 1}{sup 0} and {tilde G} are the lightest neutralino and the gravitino (the lightest supersymmetric particle), respectively. We set limits on models as a function of the {tilde {chi}}{sub 1}{sup 0} mass and lifetime, producing the world's most sensitive search for {tilde {chi}}{sub 1}{sup 0} by excluding masses up to 149 GeV/c{sup 2} for {tilde {chi}}{sub 1}{sup 0} …

A measurement of the mass of the top quark is presented, using top-antitop pair (t{bar t}) candidate events for the lepton+jets decay channel. The measurement makes use of Tevatron p{bar p} collision data at centre-of-mass energy {radical}s = 1.96 TeV, collected at the CDF detector. The top quark mass is measured by employing an unbinned maximum likelihood method where the event probability density functions are calculated using signal (t{bar t}) and background (W+jets) matrix elements, as well as a set of parameterised jet-to-parton mapping functions. The likelihood function is maximised with respect to the top quark mass, the fraction of signal events, and a correction to the jet energy scale (JES) of the calorimeter jets. The simultaneous measurement of the JES correction ({Delta}{sub JES}) provides an in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using 578 lepton+jets candidate events corresponding to 3.2 fb{sup -1} of integrated luminosity, the top quark mass is measured to be m{sub t} = 172.4 {+-} 1.4 (stat+{Delta}{sub JES}) {+-} 1.3 (syst) GeV=c{sup 2}, one of the most precise single measurements to date.

The measurement of the WW + WZ production cross section in a semileptonic decay mode is presented. The measurement is carried out with 4.6 fb{sup -1} of integrated luminosity collected by the CDF II detector in {radical}s = 1.96 TeV proton-antiproton collisions at the Tevatron. The main experimental challenge is identifying the signal in the overwhelming background from W+jets production. The modeling of the W+jets background is carefully studied and a matrix element technique is used to build a discriminant to separate signal and background. The cross section of WW + WZ production is measured to be {sigma}(p{bar p} {yields} WW + WZ) = 16.5{sub -3.0}{sup +3.3} pb, in agreement with the next-to-leading order theoretical prediction of 15.1 {+-} 0.9 pb. The significance of the signal is evaluated to be 5.4{sigma}. This measurement is an important milestone in the search for the Standard Model Higgs boson at the Tevatron.

The top quark produced through the electroweak channel provides a direct measurement of the V{sub tb} element in the CKM matrix which can be viewed as a transition rate of a top quark to a bottom quark. This production channel of top quark is also sensitive to different theories beyond the Standard Model such as heavy charged gauged bosons termed W{prime}. This thesis measures the cross section of the electroweak produced top quark using a technique based on using the matrix elements of the processes under consideration. The technique is applied to 2.3 fb{sup -1} of data from the D0 detector. From a comparison of the matrix element discriminants between data and the signal and background model using Bayesian statistics, we measure the cross section of the top quark produced through the electroweak mechanism {sigma}(p{bar p} {yields} tb + X, tqb + X) = 4.30{sub -1.20}{sup +0.98} pb. The measured result corresponds to a 4.9{sigma} Gaussian-equivalent significance. By combining this analysis with other analyses based on the Bayesian Neural Network (BNN) and Boosted Decision Tree (BDT) method, the measured cross section is 3.94 {+-} 0.88 pb with a significance of 5.0{sigma}, resulting in the discovery of electroweak produced top quarks. …

One of the central questions arising from human curiosity has always been what matter is ultimately made of, with the idea of some kind of elementary building-block dating back to the ancient greek philosophers. Scientific activities of multiple generations have contributed to the current best knowledge about this question, the Standard Model of particle physics. According to it, the world around us is composed of a small number of stable elementary particles: Electrons and two different kinds of quarks, called up and down quarks. Quarks are never observed as free particles, but only as bound states of a quark-antiquark pair (mesons) or of three quarks (baryons), summarized as hadrons. Protons and Neutrons, the constituents forming the nuclei of all chemical elements, are baryons made of up and down quarks. The electron and the electron neutrino - a nearly massless particle without electric charge - belong to a group called leptons. These two quarks and two leptons represent the first generation of elementary particles. There are two other generations of particles, which seem to have similar properties as the first generation except for higher masses, so there are six quarks and six leptons altogether. They were around in large amounts shortly …

This work presents the first comprehensive measurement of neutrino-induced charged-current neutral pion production (CC{pi}{sup 0}) off a nuclear target. The Mini Booster Neutrino Experiment (MiniBooNE) and Booster Neutrino Beam (BNB) are discussed in detail. MiniBooNE is a high-statistics ({approx} 1,000,000 interactions) low-energy (E{sub {nu}} {element_of} 0.5-2.0 GeV) neutrino experiment located at Fermilab. The method for selecting and reconstructing CC{pi}{sup 0} events is presented. The {pi}{sup 0} and {mu}{sup -} are fully reconstructed in the final state allowing for the measurement of, among other things, the neutrino energy. The total observable CC{pi}{sup 0} cross-section is presented as a function of neutrino energy, along with five differential cross-sections in terms of the final state kinematics and Q{sup 2}. The results are combined to yield a flux-averaged total cross-section of <{sigma}>{sub {Phi}} = (9.2 {+-} 0.3{sub stat.} {+-} 1.5{sub syst}.) x 10{sup -39} cm{sup 2}/CH{sub 2} at energy 965 MeV. These measurements will aid future neutrino experiments with the prediction of their neutrino interaction rates.

Trust management techniques must be adapted to the unique needs of the application architectures and problem domains to which they are applied. For autonomic computing systems that utilize mobile agents and ant colony algorithms for their sensor layer, certain characteristics of the mobile agent ant swarm -- their lightweight, ephemeral nature and indirect communication -- make this adaptation especially challenging. This thesis looks at the trust issues and opportunities in swarm-based autonomic computing systems and finds that by monitoring the trustworthiness of the autonomic managers rather than the swarming sensors, the trust management problem becomes much more scalable and still serves to protect the swarm. After analyzing the applicability of trust management research as it has been applied to architectures with similar characteristics, this thesis specifies the required characteristics for trust management mechanisms used to monitor the trustworthiness of entities in a swarm-based autonomic computing system and describes a trust model that meets these requirements.

This dissertation describes a measurement of the mass of the top quark using a method developed by G. Goldstein and R.H. Dalitz. It is based on 2.0 fb{sup -1} of data collected by the Collider Detector Facility at Fermi National Accelerator Laboratories. Di-lepton events were observed from colliding protons with anti-protons with {radical}s = 1.96 TeV in the Tevatron Collider. A total of 145 candidate events were observed with 49 expected to be from background. These events include two neutrinos which elude detection. The method begins by assuming an initial top quark mass and solves for the neutrino momenta using a geometrical construction. The method samples over a range of likely top quark masses choosing the most consistent mass via a likelihood function. An important distinguishing feature of this method from others is its lack of dependence on the missing transverse energy, a quantity that is poorly measured by the experiment. This analysis determines the top quark mass to be M{sub top} = 172.3 {+-} 3.4(stat.) {+-} 2.0(syst.) GeV/c{sup 2} (M{sub top} = 170.5 {+-} 3.7(stat.) {+-} 1.8(syst.) GeV/c{sup 2} with b-tagging).

This dissertation measures the t{bar t} production cross section at the Run II CDF detector using data from early 2001 through March 2007. The Tevatron at Fermilab is a p{bar p} collider with center of mass energy {radical}s = 1.96 TeV. This data composes a sample with a time-integrated luminosity measured at 2.2 {+-} 0.1 fb{sup -1}. A system of learning machines is developed to recognize t{bar t} events in the 'lepton plus jets' decay channel. Support Vector Machines are described, and their ability to cope with a multi-class discrimination problem is provided. The t{bar t} production cross section is then measured in this framework, and found to be {sigma}{sub t{bar t}} = 7.14 {+-} 0.25 (stat){sub -0.86}{sup +0.61}(sys) pb.

Experimental coincidence cross section and transverse-longitudinal asymmetry A{sub TL} have been obtained for the quasielastic (e,e'p) reaction in {sup 16}O, {sup 12}C, and {sup 208}Pb in constant q-ω kinematics in the missing momentum range -350 < p{sub miss} < 350 MeV/c. In these experiments, performed in experimental Hall A of the Thomas Jefferson National Accelerator Facility (JLAB), the beam energy and the momentum and angle of the scattered electrons were kept fixed, while the angle between the proton momentum and the momentum transfer q was varied in order to map out the missing momentum distribution. The experimental cross section and A{sub TL} asymmetry have been compared with Monte Carlo simulations based on Distorted Wave Impulse Approximation (DWIA) calculations with both relativistic and non-relativistic spinor structure. The spectroscopic factors obtained for both models are in agreement with previous experimental values, while A{sub TL} measurements favor the relativistic DWIA calculation. This thesis describes the details of the experimental setup, the calibration of the spectrometers, the techniques used in the data analysis to derive the final cross sections and the A{sub TL}, the ingredients of the theoretical calculations employed and the comparison of the results with the simulations based on these theoretical models.