This thesis details the simultaneous extraction of three polarisation-dependent asymmetries in the distribution of real photons from the e p → e p γ interaction and its indistisguishable deeply virtual Compton scattering and Bethe-Heitler processes at the HERMES fixed-target experiment at Desy. The data analysed were taken using a longitudinally polarised 27.57 GeV positron beam incident on a longitudinally polarised hydrogen gas target. The extracted asymmetries include two single-spin asymmetries A_UL and A_LU which depend on the polarisation of the target and beam respectively, averaged over all other polarisation states. The double-spin asymmetry A_LL dependent on the product of the beam and target polarisations is extracted for the first time. The asymmetry amplitudes extracted relate to combinations of Generalised Parton Distributions (GPDs), predominantly H and Htilde. The extracted amplitudes will be presented across the HERMES kinematic range alongside theoretical predictions from a GPD model based on double distributions. Large sin phi and cos(0phi) amplitudes are observed for A_UL and A_LL respectively, with an unexpectedly large sin(2phi) amplitude for A_UL . The results for the A_UL and A_LL asymmetries are broadly compatible with theory predictions, and the extracted A_LU amplitudes are compatible with HERMES results extracted from a significantly larger data set. It is foreseen that these results will form input to future global data-based GPD models which aim to provide a better understanding of GPDs.

That neutrinos have mass and mix is now well established experimentally. Measurements of the properties of neutrinos from both natural and man-made sources have measured the large mixing angles and mass squared differences. In order to fully understand the nature of the neutrino, and ultimately the lepton sector, a number of measurements remain to be made. The Neutrino Factory would produce an intense beam of muon neutrino (muon antineutrino) and electron antineutrino (electron neutrino) from the decay of muons creating an intense flux of neutrinos. Such a facility would be capable of constraining the already measured mixing parameters to unprecedented accuracy while achieving sensitivity to the measurement of the third mixing angle and leptonic CP violating phase unrivaled by other facilities. The golden channel is characterised by the observation of a primary muon of the opposite charge to that decaying at the source, however, since this signal is subdominant the large data sample of correct sign muons have the potential to produce backgrounds to the desired signal channel and as such understanding the cross-sections to high accuracy enables a far better understanding of the response of the detector. Making these measurements requires the optimisation of all aspects of the detectors used for the measurement of the interaction properties as well as those which search for the appearance of neutrino flavours not present at the source. Pixellated silicon detectors are capable of high resolution three dimensional track reconstruction and vertexing. In studying active pixel sensors (APS) it was sought to understand the feasibility of commercially available technology to perform vertexing at a detector positioned within 1~km of the neutrino factory source. Using such technology at this near detector would improve significantly the ability of the experiment to constrain the cross-sections of neutrinos. These measurements would be particularly important in understanding neutrino induced charm production since the decays, in particular of charged D mesons, can produce penetrating muons with the potential to confuse the extraction of the appearance of muon neutrino (muon antineutrino). The capability to observe the impact parameter of the decaying meson significantly improves the accuracy of any measurement of the charm production cross-section. A Magnetised Iron Neutrino Detector (MIND) of large mass (50-100 ktonne) has been studied as the far detector where high suppression of the beam inherent backgrounds can be achieved due to the powerful suppression of hadronic particles in iron. Particular focus has been given to the introduction of a realistic reconstruction of the signal and analysis which optimises the signal efficiency below 5 GeV which has been identified by theoretical studies as key to the accurate measurement of the oscillation parameters down to low values. Studies of this detector have led to the extraction of the expected response of the detector to both golden channel signals and demonstration of the power of such an analysis to the measurement of the remaining oscillation parameters. Using minimal assumptions in the digitization of the simulated signal, the reconstruction and analysis of a large data-set of neutrino interactions, including deep-inelastic scattering (DIS), quasi-elastic scattering (QEL) and resonant pion production (RES), in MIND has led to the extraction of response matrices predicting signal efficiency for both muon neutrino and muon antineutrino appearance with thresholds between 2-3 GeV while suppressing key beam inherent backgrounds to at or below the 10^-4 level. Such a response has been shown to open the possiblity of sensitivity to the measurement of leptonic CP violation through the measurement of the mixing complex phase delta down to theta13 of order 0.2 degrees for maximal violation and to most possible values from theta13 of order 1 degrees. Sensitivity to the measurement of theta13 and to the determination of the true mass hierarchy is maintained down to theta13 of order 0.25 degrees.

We have developed an open-path hand-held gas detector incorporating a distributed feedback InGaAs laser diode at 1.65μm. Incorporated into a hand-held transceiver unit, the emitted laser beam is backscattered from nearby surfaces, collected and focussed onto an amplified InGaAs detector using a 150mm diameter plastic Presnel lens. At ranges of 4-5metres, a typical backscattered signal is tens of nanowatts of laser light. Applying second derivative wavelength modulation spectroscopy (WMS) gives a sensitivity to methane of better than 10 parts per million over a one metre path length. Chapter 1 gives background information on existing detection methods, and explains why we chose to implement WMS. Chapter 2 discusses the various models created to justify the decision to use WMS. It also describes techniques used to help visualise escaping gas. Chapter 3 discusses the various stages of design and build of the actual prototypes, starting with a laboratory based prototype and finishing with a fully portable technology demonstrator. Chapter 4 give details of the laboratory testing undertaken in order to characterise and benchmark the system performance. Chapter 5 is concerned with the design and construction of an additional add-on scanning platform which scans the pointer instrument in order to build a 2-dimensional image of the gas escape. Chapter 6 mirrors chapter 3 in format, and discusses the various field-trials where the instruments were tested in representative conditions. Finally Chapter 7 highlights the work performed in developing a pre-production prototype and advertising the instrument to a wider market.

Little Higgs models offer an innovative solution of the naturalness problem of the Standard Model. These models contain new particles which cancel the quadratic divergences in the Higgs mass caused by the top, gauge and Higgs loops. These new particles contribute to loop induced interactions of the Higgs boson. The loop induced decays of the Higgs to gluon and photon pairs are examined in two Little Higgs models - the Littlest Higgs Model and the Schmaltz Model. The production of Higgs pairs from gluon fusion, which proceeds via heavy quark loops, is also examined in these models. Another idea considered is the multiple point principle (MPP) applied to the two Higgs doublet extension of the Standard Model. The MPP stipulates that the coupling constants will be tuned to allow the existence of a maximal number of degenerate vacua. This principle is shown to lead to a Peccei-Quinn type symmetry which naturally suppresses phenomenologically dangerous flavour changing neutral currents. Quasi-fixed points of the renormalization group are then used to derive predictions for the Higgs masses and couplings.

Lifetime measurements offer excellent opportunities for precision tests of the Standard Model of Particle Physics as well as for discovery of effects involving particles beyond the Standard Model. This thesis presents a method for measurements of lifetimes and lifetime ratios and its application to two-body hadronic final states of heavy flavour decays at LHCb. The LHCb experiment is designed to measure heavy flavour particle decays produced in proton-proton collisions at the LHC. Key to high quality vertexing is the spatial alignment of the Vertex Locator. The algorithms designed for this task, including a novel approach for the relative sensor alignment, are discussed in detail. Their performance is presented using test beam data as well as data using the first beam induced tracks from LHC. The precision of these algorithms is found to be of the order of 1-2 microns. A method for lifetime fitting using a Monte Carlo independent approach to determine a lifetime acceptance function on an event-by-event basis is presented. These acceptance functions are crucial to account for a bias caused by the trigger selection. The un-binned maximum likelihood fitter based on this method does not rely on a parametrised model for the lifetime distribution of combinatorial background. The fit of the lifetime measured in Bs->K+K- decays using a simulated data sample equivalent to an integrated luminosity of 0.1/fb would yield tau(Bs->K+K-) = (1.498+/-0.030(stat.)+/-0.005(syst.))ps with an average input lifetime of 1.500ps. A competitive measurement of DeltaGamma_s extracted from the Bs->K+K- lifetime measurement would require a data set equivalent to about 0.7/fb of luminosity. With an integrated luminosity of only about 0.03/fb it will be possible to make a competitive measurement of the D mixing parameter y_CP. This uses a lifetime ratio measurement with prompt D->h+h'- decays. A first event selection for prompt D->h+h'- decays is presented. The major hurdle for this measurement is the contribution from secondary D decays. Possible solutions are discussed.

The work in this thesis is focused on characterisation and evaluation of two classes of science grade imaging radiation detectors. The first class is Monolithic Active Pixel Sensors (MAPS). The advances in CMOS fabrication technologies over the last four decades allowed MAPS to compete with Charge-Coupled Devices (CCD) in many applications. The technology also provides relatively inexpensive ways to tailor design to suit specific application needs. It is important to understand performance capabilities of new sensor designs through characterisation and optimisation of readout parameters. In this work three MAPSs were characterised. The first one - HEPAPS4 - designed for charged particle detection, with the potential technology application in the vertex detector for the International Linear Collider. The noise of the sensor was measured to be 35±5 e, which agrees well with simulated data. The dark current was found to be 175 pA/cm2. The SNR performance for minimum ionising particles detection was demonstrated to be 40. The sensor was also evaluated for indirect detection of thermal and fast neutrons using lithium and polyethylene converters. The technology performed well in such an application with an estimated fast neutron detection efficiency of ~0.01%. The second sensor characterised – Vanilla MAPS – was designed to evaluate new techniques for fast readout, small noise and reduced image lag. The system was capable to readout 150 full frames (520x520 pixels) per second; the sensor showed 14±4 e noise and decreased image lag. The dark current was found to be ~50 pA/cm2. The back-thinned version of the sensor demonstrated dramatic improvement in quantum efficiency from 0% to 20% at 220 nm. The third device is parametric sensor eLeNA. It features 14 test structure designed to evaluated noise reduction architectures. The most promising structures showed temporal noise values as low as 6 e and 20 e fixed pattern noise. Medipix as an example of the second class of imaging detectors - hybrid pixel detectors - was evaluated in two applications. It was used as the core element of the ATLAS radiation background monitoring system. The sensors were covered with neutron converters, which extended the number of radiation types that can be detected. X-ray calibration was performed, showing excellent tolerance of all 18 devices characterised. Detection efficiencies were estimated to be ~1% for thermal and ~0.1% for fast neutrons. The second application of Medipix was mass spectrometry. The detector was place in the focal plane of a prototype mass spectrometer. 2D representation of data allowed focusing correction of the ion beam. The system was capable to detect ions in the range of 5-25 keV. The detector characterisation with broad range of ions (from Cu to Pb) showed very good abundance agreement with table data.

As a result of the need to increase the luminosity of the Large Hadron Collider (LHC) at CERN-Geneva by 2020, the ATLAS detector requires an upgraded inner tracker. Upgrading the ATLAS experiment is essential due to higher radiation levels and high particle occupancies. The design of this improved inner tracker detector involves development of silicon sensors and their support structures. These support structures need to have well understood thermal properties and be dimensionally stable in order to allow efficient cooling of the silicon and accurate track reconstruction. The work presented in this thesis is an investigation which aims to qualitatively characterise the thermal and mechanical properties of the materials involved in the design of the inner tracker of the ATLAS upgrade. These materials are silicon carbide foam (SiC foam), low density carbon foams such as PocoFoam and Allcomp foam, Thermal Pyrolytic Graphite (TPG), carbon/carbon and Carbon Fibre Reinforced Polymer (CFRP). The work involves the design of a steady state in-plane and a steady state transverse thermal conductivity measurement systems and the design of a mechanical system capable of accurately measuring material stress-strain characteristics. The in-plane measurement system is used in a vacuum vessel, with a vacuum of approximately 10¡5 mbar, and over a temperature range from -30±C to 20±C. The transverse and mechanical systems are used at room pressure and temperature. The mechanical system is designed so that it measures mechanical properties at low stress below 30MPa. The basic concepts used to design these measurement systems and all the details concerning their operations and implementations are described. The thermal measurements were performed at the Physics and Astronomy department of the University of Glasgow while the mechanical measurements were performed at the Advanced Materials Technology department, at the Rutherford Appleton Laboratory (RAL). Essential considerations about the measurement capabilities and experimental issues are presented together with experimental results. The values obtained for the materials with well understood properties agree well with the values available in the literature, confirming the reliability of the measurement systems. Additionally, a Finite Element Analysis (FEA) is performed to predict the thermal and mechanical properties of PocoFoam. The foam is created by generating spherical bubbles randomly in the computational tool MatLab according to the topology of PocoFoam. The model is transferred to the CAD program Solid works to be extruded and be transformed into PocoFoam. It is later on transferred to the FEA tool ANSYS to be analysed. Simulations of a specimen of density equal to 0.60g/cm3 are performed and the results are compared with the values measured for a specimen of density equal to 0.56g/cm3. The simulated results agree within 32% with the experimental values. The experimental results achieved in the studies undertaken in thesis have made a considerable contribution to the R&D of the stave design by helping to understand and optimise the current stave design and explore new design possibilities. The stave is a mechanical support with integrated cooling onto which the silicon sensors are directly glued.

Albert Einstein in 1916 predicted the existence of a Gravitational Wave in his General Theory of Relativity. These waves, which propagate at the speed of light transmit gravitational information through the Universe. Since its prediction by Einstein, astronomers and physicists have searched for them and developed method to detect them. Though so far unsuccessful, the search of Gravitational waves goes on and great efforts are being made to develop the most sensitive detectors yet in the hope of that first detection. Currently ground based detectors are limited by coating Brownian thermal noise due to excitation of the reflective coatings applied to the test masses. Through measurement of mechanical loss of a material the magnitude of the Brownian thermal noise can be determined. It is necessary to determine the root cause of mechanical loss in current coatings (Ta2O5¬ and SiO2). Work towards this goal is taking place on multi paths, directly, through characterisation of mechanical loss and indirectly through microscopy studies to determine the structural cause. In this thesis, the effect of TiO2 doping and heat treatment of Ta2O5 has been investigated. It has been previously shown that a TiO2 doping of Ta2O5 reduces the mechanical loss and that, that reduction is at a maximum at 30% TiO2. It has been determined through Electron Diffraction experiments that the structure of TiO2 doped Ta2O5 becomes more homogenous up to 30% doping. Through computation modelling of these structures using Density Functional Theory it has also been determined that the abundance of TiTaO2 ring formations also maximises at 30% doping. Further modelling has also determined that the TiTaO2 rings are more flexible that their counter parts of Ta2O2 and Ti2O2. From this it has been hypothesised that the overall flexibility of a structure is a strong component of the mechanical response of the structure. Hence by increasing the flexibility through TiO2 doping the mechanical loss (as Thermal Noise) is decreased similarly and this response would also be expected using similarly flexibility improving dopants.

In recent years there has been great interest in the applications of the interaction of the phase and intensity of laser light in atomic vapours. The generation of light beams with arbitrary phase and intensity patterns can now be easily achieved by using Spatial Light Modulators (SLMs). The transformation of quantized units of phase information to atomic vapours has implications in the fields of quantum optics for the realisation of sources of entangled photons, optical switching, and quantum information storage. Spatially shaped beams with non-trivial intensity geometries have found use in single atom quantum well traps and for the enhancement of density of standard Magneto Optical Traps. The work in this thesis is focussed around two main pro jects, involving the interaction of holographically shaped light beams with cold trapped atoms and with a hot atomic vapour respectively. An enhancement to the previously investigated technique of a SPontaneous force Optical Trap SPOT of 87 Rb is presented here which aims to solve various issues which naturally arise from compressing cold atoms in a Magneto Optical Trap (MOT) such as unavoidable heating during the compression. High density/high atom number traps are highly sought after in many experiments for more efficient transfer of atoms to Bose Einstein Condensates and for improved quantum storage capabilities in cold atom traps. The highest density achieved in our SPOT was 2.5 × 10^12 atoms cm−3 for 2 × 10^8 atoms at a temperature of approximately 100µK. This represents almost 2 orders of magnitude increase in density from the standard MOT setup with no adverse heating of the trap while maintaining 75% of the atoms. In the second part of this work hot atomic vapours are utilized for the efficient transfer of orbital angular momentum information from near infra-red pump fields, driving from 5S_1/2 to 5D_5/2 on a two-photon transition, to a cascade from 5D_5/2 to 6P_3/2 to 5S_1/2 generating 5230nm light and a coherent blue, 420nm, beam respecitively. This generation is performed using four wave mixing in 85 Rb. We observe the complete conversion of all input quantum information, the Orbital Angular Momentum (OAM) from the pump fields to the blue. In addition we show the additional phase coherence effects of this experiment through the use of simple superpositions of Laguerre-Gaussian (LG) modes showing that the process is indeed quantum in nature. A theoretical basis for the transfer of all OAM information to only the 420nm beam is also discussed here.

This thesis captures a numerical study of the interplay between disorder and electron-electron interactions within the integer quantum Hall effect, a regime where the presence of a strong magnetic field and two-dimensional confinement of the electrons profoundly affects the electronic properties. Prompted by recent novel experimental results, we particularly emphasise the behaviour of the electronic compressibility as a joint function of magnetic field and electron density, which appears to be insufficiently accounted for by the widely used independent-particle model. Our treatment of the electron-electron interactions relies on the Hartree-Fock approximation so as to achieve system sizes comparable to the experimental situation. We find numerical evidence for various interaction-mediated effects, such as non-linear screening, local charging, and g-factor enhancement. Important implications for the phase diagram may arise, although a study of the scaling of the participation ratio seems to imply a universal critical behaviour independent of interactions. Furthermore, we examine the Hall conductivity in a similar fashion, which also displayed interaction-promoted features in transport measurements. Our mesoscopic simulations only reproduce some of the observed features, suggesting the presence of effects beyond numerical tractability. Finally, we model scanning tunneling spectroscopy experiments and systematically investigate the influence of the tip induced potential as well as the interactions among the electrons. Our results show a strong dependence on the filling factor and may greatly assist the interpretation of such spectroscopy data.