Generalised Parton Distributions (GPDs) provide a theoretical framework that promises to deliver new information about proton structure. In the impact parameter interpretation, they describe the substructure of the proton in terms of its quark (and gluon) constituents in three dimensions: two transverse spacial dimensions and one longitudinal momentum dimension. Through Ji’s sum rule, they offer a means by which to determine the total angular momentum contribution of quarks to the proton’s spin of h ̄ /2. GPDs are directly related to Compton Form Factors (CFFs), which are distributions that are measurable us- ing Deep Exclusive Scattering (DES) processes such as deeply virtual Compton scattering (DVCS). DVCS is characterised by the scattering of a single photon with large virtual- ity off a single quark (or gluon) inside the proton, resulting in the production of a hard photon: γ ∗ p → γ p′ . In this work, data recorded with the CLAS detector at Jefferson Laboratory during the EG1DVCS experimental run were analysed. This experiment ran for over 80 days with a longitudinally polarised electron beam and a solid NH3 target containing longitudinally polarised protons. The resulting data set accommodated pre- cise measurements of DVCS beam, target and double spin asymmetries, each of which is sensitive to different combinations of CFFs. The final results presented here are fits to these three asymmetries, which were performed using the Extended Maximum Like- lihood method. It is intended that these results will be used in the future, along with other DES asymmetry and cross-section measurements, to constrain CFFs and thus move towards a more complete understanding of the structure of the proton.

The PhD project aimed to develop methodologies for optimisation of automatic tube current modulation (ATCM) performance for the four most important computed tomography (CT) scanner manufacturers (Toshiba, GE, Philips and Siemens scanners). Since the human body to which ATCM response is elliptical in shape, the project started with an investigation of differences between dosimetry in cylindrical and elliptical phantoms. The ATCM systems modulate the tube current in both the x-y plane and z-axis, therefore phantoms made from multiple sections of different size ellipses were designed for quality control of the ATCM performances and evaluated by comparing with a conical phantom developed by imaging performance and assessment of CT (ImPACT) evaluation centre, UK. In order to link the project into patient dose optimisation, CT scanners in which patient doses were high were identified and the link with patient size evaluated. Since the large variations in patient dose may be influenced by scan parameters, the phantom developed was used to carry out measurements on CT scanners and investigate some factors and attribute reasons for the high doses. Finally changes in CT scanner protocols were recommended. The results from the elliptical phantom showed that the doses in the centre and anterior were larger than in the cylinder, while doses in the lateral periphery were similar. Differences in ratios of doses between the two phantoms for different CT scanners are linked to the beam profiles produced by the individual bow tie filters. Phantoms made from multi elliptical sections demonstrated similar trends for the Philips and Siemens ATCM systems. However, the abrupt changes in attenuation provoked the ATCMs to increase tube current aggressively with the GE and Toshiba systems. A phantom like a wedding cake with broader sections and smaller differences in attenuation circumvented these effects. The volume weighted CT dose index (CTDIvol) increased significantly with patient size for Toshiba and GE scanners whilst the changes for Siemens and Philips scanners were less marked. However, the use of Philips the D-DOM ATCM option led to a significant increase in patient dose. The reconstruction filter and image thickness are major factors influencing patient dose for the Toshiba CT scanner.

A comparison of the two statistical frameworks, MCLimits and RooStats is presented in relation to the statistical combination of the decay channels of the Standard Model Higgs boson using data collected by the ATLAS experiment in the period up to the end of the 2012 LHC run. A wrapper mechanism designed to allow the RooStats model and data containers to be compatible with MCLimits is described. This interface is used to produce statistical plots for single channel and full combination Higgs searches. The MCLimits and RooStats results are compared and contrasted, showing good agreement throughout the mass range, acting as a double check of the published results. The extension of the Higgs mass search range above 600 GeV is discussed, including a summary of the Complex Pole Scheme. The implementation of the Complex Pole Scheme is necessary in analyses considering a heavier Higgs-like particle. A framework was created to adjust existing Monte Carlo samples to give an approximation of the Complex Pole Scheme. This allowed quick implementation of this theory and studies of the effects on the existing analyses without the large scale tasks of rerunning all relevant Monte Carlo samples. The framework was adapted to be as general as possible to allow for the inclusion and study of other theories and modifications.

Orbital angular momentum (OAM) is one of the most recently discovered properties of light, and it is only in the past decade its quantum properties have been the subject of experimental investigations and have found applications. Unlike polarization, which is only bidimensional, orbital angular momentum provides, with relative ease, unprecedented access to a theoretically unbounded discrete state space. The process of spontaneous parametric down-conversion has long been used as a source of two-photon states that can be entangled in several degrees of freedom, including OAM. In this thesis, the properties of the natural OAM spectrum associated with the entangled states produced by parametric down-conversion were investigated. Chapters 2 and 3 describe the production and detection of tunable high-dimensional OAM entanglement in a down-conversion system. By tuning the phase-matching conditions and improving the detection stage, a substantial increase in the half-width of the OAM correlation spectrum was observed. The conjugate variable of OAM, angular position, was also considered when examining high-dimensional states entangled in OAM. In order to efficiently determine their dimension, high-dimensional entangled states were probed by implementing a technique based on phase masks composed of multiple angular sectors, as opposed to narrow single-sector analysers. Presented in chapter 4, this technique allows the measurements of tight angular correlations while maintaining high optical throughput. The states so produced were then used for a number of applications centred around the concept of mutually unbiased bases. One can define sets of mutually unbiased bases for arbitrary subspaces of the OAM state space. Two bases are mutually unbiased if the measurement of a state in one basis provides no information about the state as described in the other basis. Complete measurements in mutually unbiased bases of high-dimensional OAM spaces are presented in chapter 5. Measurements in sets of mutually unbiased bases are integral to quantum science and can be used in a variety of protocols that fully exploit the large size of the OAM state space; we describe their use in efficient quantum state tomography, quantum key distribution and entanglement detection. Caution is however necessary when dealing with state spaces embedded in higher-dimensional spaces, such as that provided by OAM. Experimental tests of Bell-type inequalities allow us to rule out local hidden variable theories in the description of quantum correlations. Correlations inconsistent with the states observed, or even with quantum mechanics, known as super-quantum correlations, have however been recorded previously in experiments that fail to comply with the fair-sampling conditions. Chapter 6 describes an experiment that uses a particular choice of transverse spatial modes for which super-quantum correlations persist even if the detection is made perfectly efficient. The sets of modes carrying OAM allow a complete description of the transverse field. The ability to control and combine additional degrees of freedom provides the possibility for richer varieties of entanglement and can make quantum protocols more powerful and versatile. One such property of light, associated with transverse modes possessing radial nodes in the field distribution, can be accessed within the same type of experimental apparatus used for OAM. In chapter 7, the radial degree of freedom is explored, together with OAM, in the context of Hong-Ou-Mandel interference.

The associated Z vector boson production rate of the Standard Model Higgs boson has been measured in decays into two b quarks, with the Z boson decaying into an electron or muon pair in the ATLAS detector at the Large Hadron Collider (LHC). The associated Z vector boson production cross section in the Standard Model is almost two orders of magnitude smaller than the dominant Higgs boson production cross section from gluon fusion. Proton-proton collision data at a centre-of-mass energy of 8 TeV delivered by the LHC with the ATLAS detector corresponding to an integrated luminosity of 13 fb−1 has been analysed. A Higgs boson produced via associated production with a Z vector boson is excluded with a 95% confidence level in a mass range between 110 to 130 GeV at 6 to 11 times the Standard Model cross section, respectively.

The work in this thesis is focused on the study of CdTe/CdZnTe pixellated detectors. During this research, three main aspects have been covered in the development and application of these detectors. These broadly describe the fabrication process, characterisation of energy spectrum and imaging performance, and application of these detectors in industrial X-ray tomography. The first topic to be discussed in detail is the fabrication process of CZT pixellated detectors. This is a process that involves many steps, such as cutting the sample, cleaning the substrate, writing a masking pattern with e-beam lithography, photolithography, cleaning the surface using oxygen ash, metallisation and removing the resin in the development stage. However, these stages were grouped into three major steps to give a clearer image on what was going on throughout the fabrication process. They are grouped as sample preparation, pixellated structure deposition and sample passivation. The dry ash processing had been carried out in the James Watt Nano Fabrication Centre at Glasgow University. The motivation for the development of the dry ash process was to reduce the level of leakage current on the surface of the device so that a good energy spectrum resolution could be obtained. The research showed that a passivation technique using a layer of SiN as well as an oxygen plasma oxidation layer provided low leakage current in the pixel and lower interpixel leakage current. A good performance in energy spectrum was achieved after performing passivation. The FWHM of Co-57 is 10.78 keV where energy resolution is 8.8%. The second area covered in this thesis is the energy spectrum and imaging performance of pixellated CdTe Timepix detector. Two pitches of pixel have been studied namely, 110 µm pitch and 55 µm pitch. The work on characterisations has been performed with polychromatic and monoenergetic beams of X-rays. In both the Counting mode and ToT (Time over Threshold) mode it was discovered that there were large effects on performance due to charge sharing and fluorescence. In terms of image quality the result of MTF was found to be as expected, around half the contrast transfer (30%) recorded for 110 µm compared to 55 µm pixel detector at 4 lp/mm. Another field of interest explored was the defect factor. For this to be achieved studies had been performed in positive and negative bias of CdTe Timepix detector. The results showed that the presence of defects in the material affects the performance of the energy resolution of CdTe Timepix detector. The third area covered in this thesis was the study of CdTe Timepix detector for use in Industrial X-ray tomography. To give the sensor the best performance it could offer in capturing images for industrial use, work had been carried to optimise the technique for producing good quality images. The hardware setup involved the careful alignment all of the components of the system and the introduction of a collimator. In addition the sofware software it dealt with the flat field correction, noise filter and data projection algorithm. The results show that the CdTe Timepix detector can be used as a good detector for X-ray tomography. Here, the 3D of volume rendering studies had been performed to a pencil as a sample and voltage regulator. The result of the pencil image in volume rendering showed that CdTe Timepix detector had successfully provided good image for different density profile of material (paint coating, wooden and carbon). Not only that, another important finding besides the excellent image produced was that the effect of beam hardening, ring artifact and metal shrank artifact in tomogram of voltage regulator had been eliminated successfully.

This thesis contains measurements of temperature dependent mechanical loss, Young's modulus, and coefficient of thermal expansion of various amorphous optical coating materials of interest to gravitational wave detectors. The materials focused upon here are hafnia and titania-doped tantala. Measurements of the mechanical loss of hafnia indicate that at temperatures below 100 K, hafnia with heat treatments between As Deposited and 400 C have lower loss than tantala. However, the hafnia was found to be partially crystalline, which must be removed in order to meet the requirements of gravitational wave detectors. This may also improve the mechanical loss. Loss measurements of 25 and 55% As Deposited titania-doped tantala indicate that the activation energy of the two-level system loss mechanism is greatly different between the two doping concentrations. The Young's modulus of the coating materials was carried out using nano-indentation. The Young’s modulus of un-doped tantalum dioxide is reduced with increasing heat-treatment until the sample crystallizes between 600 and 800 C. The 25% doped samples exhibit similar trends, while the 55% doped samples have the opposite trend. Additional measurements have also been made for IBS hafnia and amorphous silicon coatings. The coefficient of thermal expansion was measured using a thermal bending setup, which extracts a combination of Young's modulus and coefficient of thermal expansion. The Young's modulus from the nano-indentation measurements was then used to extract the thermal expansion. For the 25 and 55% tantalum dioxide doped coatings did not vary with heat-treatment; however, it did appear to vary for the hafnia coatings.

The LHCb detector at CERN is scheduled to undergo an upgrade during the second long shutdown of the LHC. As part of this upgrade, the vertex detector (VELO) will be replaced with a new hybrid pixel detector, based on an evolution of the Timepix ASIC. The performance of this detector should improve upon that achieved by the current VELO, in addition to facilitating the complete detector readout at 40 MHz. As part of the preparation for this upgrade, this thesis presents the results of studies carried out on the single hit resolution of silicon hybrid pixel detectors. The development of a particle beam telescope has been carried out to allow these studies, shown to operate with track rates in excess of 45 kHz and with a pointing resolution at the device under test of less than 2 μm. A wide range of sensor types, thicknesses and resistivities have then been tested under different operating conditions and the results presented, with single hit resolutions varying between 4 μm and 12 μm depending on the conditions and incident angle. The resistivity of the devices is observed to have a significant effect on the single hit resolution, with high resistivity substrates allowing operation at lower bias voltages. This facilitates increased charge sharing, and the corresponding improvement in resolution. At sufficiently large incident angles however, the resolution becomes independent of the electric field, being instead dominated by the sensor geometry and variations in the charge deposited along the track length. No significant differences were found between the various detector technologies (n-on-n, n-on-p and p-on-n) though a difference in performance is expected for low-voltage operation of higher resistivity samples. A simplified model of the physical processes contributing to the detector resolution has been constructed, shown to reasonably reproduce the observed resolution as a function of angle and bias voltage. This model is extrapolated to potential future directions in the design of pixel sensors, highlighting the differences between various technology choices. The integration of the ATLAS FE-I4 ASIC into the telescope has been carried out, and the performance of an unirradiated planar silicon sensor was shown in order to verify this. Efficiency measurements show that the device is fully efficient in the angular range measured. The tracking performance of two irradiated sensors mounted on FE-I4 ASICs has been investigated, in addition to the mapping of collected charge over the pixel unit cell under various biasing conditions and at varying incident angles with respect to the incoming particles. For the sample irradiated to 2e15 1 MeV neq /cm2 the single hit resolution was 12.5 μm at perpendicular incidence, dropping to 8 μm at 22 degrees. The sample irradiated to 4e15 1 MeV neq /cm2 was found to have a resolution of around 13.5 μm, which remained relatively insensitive to the incident track angle. The conclusions drawn suggest that the upgraded VELO detector will be able to overcome the difficult radiation environment if it is able to reach the high voltage operation required. The implementation of these observations in the LHCb simulation environment has allowed some initial studies on the likely degradation of the detector performance to take place, showing that the high tracking efficiency (99.4 % for Long tracks) is likely to be maintained throughout the full lifetime of the upgrade. The impact parameter resolution was not observed to vary significantly. These studies have been carried out alongside simulations to gauge the expected compression that can be achieved in the data transmission of the VELOPix ASIC. Different designs of the front-end have been implemented, leading to the adoption of binary readout for the upgraded VELO. The uniformity of the pixel pitch across the detector has additionally been used to show the sensitivity of the system to multiple scattering, shown to be a credible tool with which to control the event reconstruction in the online LHCb trigger. A reduction of the number of VELO tracks passed to the forward reconstruction of almost 50 % has been shown, for the loss of only 5 % of tracks with momentum above 20 GeV/c. This could potentially replace the lifetime biasing cuts currently envisaged in the trigger.

The damage introduced into an InGaAs/InGaAsP quantum well structure during CH4/H2 reactive ion etching (RIE) processes was measured, for plasma powers from 20 W to 100 W, using low temperature photoluminescence. The damage depth profile is estimated to be around 12 nm - 70 nm after annealing at 500 °C for 60 seconds using a rapid thermal annealer (RTA). A reduced damage RIE process has been developed to fabricate InGaAs/InGaAsP multi-quantum well ridge waveguide lasers. The performance of these lasers has been compared to that of lasers fabricated from the same epilayer using wet etching to form the ridge. The resultant threshold currents were essentially indistinguishable, being 44.5 mA and 43 mA respectively for dry and wet etched lasers with 500 μm long laser cavities. Quantum well intermixing in the InGaAs/InGaAsP material system was demonstrated using two techniques. The first was a laser irradiation process, which combines irradiation by continuous wave and Q-switched pulsed Nd: YAG lasers. Differential shifts up to 70 nm have been obtained. The second was a plasma process which involves sputtering a thin layer of Si02 and subsequent high temperature annealing using either a CW laser or rapid thermal annealer (RTA). Differential blue-shifts of the bandgap of up to 120 nm were obtained. The bandgap shift in the control regions is very insignificant. Measurement of the spatial selectivity of this technique shows that the spatial resolution is better than 50 μm. The design, fabrication and characterisation for 3-dB MMI couplers were carried out using both as-grown (peak emission wavelength of 1.48 μm) and bandgap widened material. The measured results show good agreement with the design. A splitting ratio of around 0.12 dB (51: 49) has been achieved for an MMI section length of 470 gm. Low loss waveguides have been fabricated using the laser process. A loss as low as 2.1 dB/cm was obtained for an operation wavelength of 1.556 um. Extended cavity ridge lasers (ECL) in InGaAs/InGaAsP multiple-quantum well structures have been successfully fabricated using the two QWI technique developed. The increases in threshold current were only 10 mA and 8 mA for cavity length of 800 4m active section and 1000 μm passive section, compared to the all active lasers with cavity length of 800 μm, and the losses in the passive sections of ECLs were calculated which were 2.4 cm-1 and 4.4 cm-1, for the two processes, respectively. Considerable theoretical work was carried out, which included the calculation of the optical confinement and gain in the InGaAs/InGaAsP MQW structure used throughout this thesis. Modelling of the intermixing of quantum wells was also performed and the results indicate that the changes of bulk bandgap energy are mainly responsible for the blue-shift of the photoluminescence.

The aim of this work was to study the crystal growth of indanthrone during the pigmentation process. The colouring properties of a pigment are dependent on the chemical and crystallographic structure of the pigment. However, other factors are known to affect these properties including particle size, particle size distribution and level of dispersion in the chosen application medium. The parameters which affect the growth of the pigment particles were investigated with the emphasis placed on the mechanism by which growth took place. The final form of the crystals after growth was also investigated in this thesis. High and low magnification imaging and diffraction were studied on the CTEM (conventional transmission electron microscope) whilst PEELS (parallel electron energy loss spectroscopy) and DPC (differential phase contrast) studies took place on the VG HB5 STEM (scanning transmission electron microscope). In addition to these studies, x-ray diffraction and surface area analysis techniques were employed. The low magnification CTEM work gave good information on the size, shape and size distribution of the pigment particles and enabled detailed analysis of the level of growth attained under varied reaction conditions. Parameters varied during these reactions included choice of solvent, solvent concentration, reaction time and the method used for removing the solvent. Methyl benzoate and nitrobenzene were found to be effective in promoting crystal growth in indanthrone whilst isopropanol proved to be extremely ineffective. The rate of growth was found to be affected by, among other things, the concentration of the solvent and the time it was in contact with the pigment. The most likely method of growth has been identified as ripening followed by coalescence. Initially, larger particles grow at the expense of the smaller particles - the smaller ones go into solution and are then able to aid the growth of the larger particles.