It is now largely accepted that dark matter, and more specifically, Weakly Interacting Massive Particles (WIMPs), constitute the majority of the mass in our Universe. Within this thesis are presented: (i) an overview of the motivation and evidence for the existence of dark matter; (ii) a detailed discussion of direct detection techniques and a worldwide review of WIMP search experiments; and (iii) new experimental measurements and complementary detailed numerical simulations, carried out by the author, to determine the performance of DRIFT experimental technology. Collectively, this work explores the capability of DRIFT technology to detect dark matter, and in doing so, to resolve one of the key open questions of contemporary science. The DRIFT programme consists of an array of direct dark matter search detectors located in the Boulby mine. An important limitation to the experiment is the neutron and gamma-ray background. Experimental work presented here has determined the U and Th content of the cavern rock to be 66±6 ppb and 145±13 ppb respectively, clarifying ambiguities in previous estimations. Through the use of a Monte Carlo simulation the neutron and gamma-ray background experienced by DRIFT has been determined and the experimental implications assessed. In addition, the activity of the main neutron calibration source used to calibrate DRIFT modules has been measured and was found to be 11600 n s−1±5% on the date of exposure, resolving an earlier discrepancy. Analysis of experimental data has confirmed that the technology employed by DRIFT detectors has the capability to provide directional information of recoiling nuclei at the low energies of interest to dark matter searches. A Monte Carlo simulation has then been employed to determine the WIMP-nucleon sensitivity achievable using DRIFT detectors of the present performance, also examining what would be achievable if this was supplemented by a realistic active neutron veto detector. It is found that a CS2-filled DRIFT type detector running at a 500 NIP threshold ( 16 keV and 27 keV for C and S recoils respectively) for 300 kg years, and surrounded by the proposed veto scheme, would expect to observe a background of six un-vetoed events. The minimum positive signal above this background (90% C.L.) would correspond to a WIMP-nucleon sensitivity limit of 1.75×10−9 pb. This identifies the realistic limit of what can be achieved using gaseous CS2 as a target medium. An investigation into the limits achievable using a similar array in which DRIFT modules act as self-vetoing detectors is also examined providing insight into the future development and operation of the DRIFT programme.

<p> Historically, the thermal photon inverse slope parameter has been interpreted as the thermalization temperature of the QGP. Observation of the thermal photon spectrum in nucleus-nucleus collisions at the ALICE and PHENIX experiments obtain the inverse slope parameter, but the obtained values are inconsistent with the thermalization temperature predicted by the hydrodynamic model. It has therefore been argued that the inverse slope parameter is not representative of the true QGP thermalization temperature because not all thermal photons are emitted at thermalization. This research will probe this assertion using an investigation of flow and nuclear suppression of thermal photons from ALICE Pb-Pb collisions at &radic;<i>s_NN</i> = 2.76 TeV and comparison to p-p data at &radic;<i>s_NN</i> = 2.76 TeV.</p>

The LHCb experiment at CERN is nearing completion and is expected to begin operation in 2008. It will make precision measurements of Charge-Parity in the B meson system. Two Ring Imaging Cherenkov detectors provide excellent charged particle recognition, particularly in their separation of kaons and pions. This thesis outlines the production and testing of Hybrid Photon Detectors, used to measure Cherenkov light in the Ring Imaging Cherenkov detectors. We also report an analysis of the rare decay Bos -> ØØ.

In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function $g\sbsp{1}{n}(x,Q\sp2)$ of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized $\sp3$He target. The high beam energy allowed us to extend the kinematic coverage compared to the previous SLAC experiments to $0.014\leq x\leq0.7$ with an average $Q\sp2$ of 5 GeV$\sp2.$ We report the integral of the spin dependent structure function in the measured range to be $\int\sbsp{0.014}{0.7}dx\ g\sbsp{1}{n}(x,5\ {\rm GeV}\sp2)={-}0.036\pm0.004({\rm stat}.)\pm0.005({\rm syst}.).$ We observe relatively large values of $g\sbsp{1}{n}$ at low x that call into question the reliability of data extrapolation to $x\to0.$ Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. We perform a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions $g\sbsp{1}{p}$ and $g\sbsp{1}{n}$ paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, we evolve the data to $Q\sp2$ = 5 GeV$\sp2,$ determine the first moments of the polarized structure functions of the proton and neutron, and find agreement with the Bjorken sum rule.

Experiment E690 at Fermilab recorded 5.5 billion $p + p \to p + X$ events using an 800 GeV/c proton beam and a liquid hydrogen target, during the 1991 fixed target run. We use a 0.5 billion subset of this sample, to study the reaction $p + p \to p\sb{s}(\pi\sp+\pi\sp-)p\sb{f}$ for dipion invariant mass between threshold and 2.3 GeV/c$\sp2.$ We perform a partial wave analysis for dipion invariant mass between threshold and 1.5 GeV/c$\sp2.$ The assumption of S-wave dominance near threshold is sufficient to determine a single, continuous solution throughout the considered mass spectrum. Precision measurement of the production amplitude aids the mapping the low lying meson spectrum. Other possible studies using this data sample and analysis technique are: (1) the extension of the amplitude analysis above the 1.5 GeV/c$\sp2$ mass region using a the full event sample, and (2) the study of the produced amplitudes as a function of the relative angle between the two proton planes.

Results are presented on a study of resonant structure in the $\omega\pi\sp0$ and $\omega\eta$ final states produced in $\pi\sp-p$ interactions at 18 GeV/c where $\omega\to \pi\sp+\pi\sp-\pi\sp0,\ \pi\sp0\to 2\gamma,$ and $\eta\to 2\gamma.$ Final states such as $\omega\pi\sp0$ and $\omega\eta,$ which contain a vector meson are allowed in the extended flux-tube model for the decay of hybrid mesons. For the $\omega\eta$ final state, the data exhibit the well-known $b\sb1$(1235) and $\rho\sb3$(1690) resonances. A one-pion exchange mechanism is clearly seen for the $\rho\sb3$(1690). The result of a partial wave analysis for the $\omega\eta$ final state finds a new $1\sp{+-}$ meson state $h\sb1$(1540) with a mass $M = 1542\pm 13$ MeV and a width $\Gamma = 285\pm 30$ MeV, which shows phase motion relative to the $\omega$(1600). The decay mode of $\omega(1600)\to \omega\eta$ has not been previously reported.

The longitudinal relaxation time T$\sb1$ is calculated for a dilute Fermi gas. We include the possibility of arbitrary degrees of polarization P, and uniform external magnetic fields. At low temperatures T$\sb1$ is proportional to T$\sp{-2}$ for the unpolarized gas in agreement with earlier calculations. For a polarized system in zero applied field the separation between up and down Fermi spheres provides an open channel in phase space for spin flipping processes. As temperature is reduced to zero T$\sb1$ levels off and approaches a constant value which depends sensitively on P, leading to much smaller values of T$\sb1$ than in the unpolarized case. For relaxation in a uniform external field H, Zeeman energy conservation during spin flipping interactions essentially shifts the location of the T$\sp{-2}$ behavior from zero polarization to the polarization P(H) which would be produced in equilibrium with the external field H. When the initial polarization of the system is different from P(H), T$\sb1$ again approaches a constant value which is equally sensitive to the initial polarization as temperature is reduced to zero. We apply our calculations to the case of dilute $\sp3$He-HeII solutions. We also consider the calculation of density dependent corrections to T$\sb1$ for unpolarized, or weakly polarized $\sp3$He-HeII using the long wavelength limit of the Bardeen-Baym-Pines interaction as a form for the spin independent part of the $\sp3$He-$\sp3$He interaction. Owing to the positive sign of the antisymmetric Landau parameter $\rm F\sbsp{o}{a}$ in dilute $\sp3$He-HeII Fermi Liquid interactions act to screen the magnetic dipole interactions which cause relaxation. To lowest order in density we find that the relaxation rate 1/T$\sb1$ is reduced by factor $\rm (1 - 3F\sbsp{o}{a})$ which compares favorably with recent calculations of T$\sb1$ for pure $\sp3$He.

Two areas of nonleptonic weak interactions are examined: parity-violation in nucleon-nucleon interactions including $\Delta$ excitations, and strangeness-changing hypernuclear decay processes. In both cases we utilize SU(6)$\sb{w}$-based quark model pictures to describe the weak hadronic physics. In the first part of this dissertation we develop an effective parity-violating Hamiltonian for the weak interactions of $\Delta$'s with hadrons and mesons. We evaluate weak parity-violating $\Delta$-$\Delta$-meson and $\Delta$-nucleon-meson vertices for $\pi$, $\rho$, and $\omega$ mesons, thus extending previous work involving only nucleons and mesons. The second part of this dissertation presents the results of calculations for several observables involving the decay of hypernuclei. We examine the model dependence of these observables by considering several variations of the model and its parameters.

Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2008. / Title from PDF t.p. (viewed on Jul 28, 2009). Source: Dissertation Abstracts International, Volume: 69-12, Section: B, page: 7573. Adviser: Michael Snow.

Thesis (M.S. in Physics)--Naval Postgraduate School, December 1990. / Thesis Advisor(s): Weaver, Wm. Bruce. Second Reader: Cleary, David D. "December 1990." Description based on title screen as viewed on March 29, 2010. DTIC Identifier(s): Atmosphere Models, Photons, Parameters, Photosphere, Theses. Author(s) subject terms: Simulation, Solar absorption lines, Radiative transfer theory. Includes bibliographical references (p. 56-57). Also available in print.