K+Λ photoproduction provides the best possibility for a model independent extraction of the photoproduction process and contributing resonances. To do this, it is vital that cross section measurements are well understood. This thesis presents pγ K+Λ differential cross sections from the reaction threshold, to an invariant centre of mass energy of 1.87 GeV. The data was taken at MAMI-C electron microtron facility in Mainz, Germany, during July 2007 and April 2009. The 1.5 GeV MAMI-C electron beam was used to produce an energy tagged bremsstrahlung photon beam with a maximum energy of 1.4 GeV and an intensity of 105γs-1MeV-1. The beam impinged upon a liquid hydrogen target, with reaction products detected in two segmented calorimeter arrays; the Crystal Ball detector and TAPS. This work pioneers a new method of K+ detection in segmented calorimeters, in which the K+ was identified from the signature of its weak decay inside the crystals of the calorimeter. This proved to be an excellent method of isolating K+ and accessing strangeness photoproduction channels, with good agreement between experimental and Geant4 simulated data. A novel method in seperating K+Λ and K+Σ0 final states was also developed by identifying the photon from the decay: Σ0 → Λγ. The intense photon beam at the MAMI-C facility enabled differential cross section data with greater invariant mass resolution than previous measurements. The new measurement near threshold imposes important constraints to effective field theories based on the approximate chiral symmetry of QCD. At higher centre of mass energies it also addresses the current problem of discrepant data sets and will form an important constraint on partial wave analysis for the nucleon excitation spectrum. As such, this work contributes to a major world wide programme aiming to extract the excitation spectrum of the nucleon and to understand the dynamics and interactions of its constituents. The greater statistics near threshold, and particularly at backwards K+ centre of mass angles will give new valuable constraints to contributions from meson and hyperonic resonances on the reaction mechanism. The high resolution of the photon beam (approximately 2 MeV) also allows the first search for narrow resonances coupling to KΛ final states. The differential cross sections give good agreement with Kaon-MAID partial wave solutions, apart from at backward angles close to threshold, where the data is lower. Near threshold, the data agrees with calculations from the chiral unitary framework of Borasoy et al, tending to be in better accordance with the model than previous data. No strong structure from potential narrow resonance states was observed over the centre of mass energy region of 1650-1700 MeV, where narrow structure has been observed in recent η photoproduction of the neutron.

A large acceptance polarimeter has been designed to measure recoil polarisation in pseudoscalar (Jπ=0−) meson photoproduction reactions. The device was installed at the MAMI facility at the Institut für Kernphysik in Mainz, Germany. A racetrack microtron provided a longitudinally polarised 1.5 GeV electron beam, which impinged on a 12 μm copper radiator, producing a beam of circularly polarised Bremsstrahlung photons with energies between 400-1400 MeV. The electrons were then momentum analysed in the Glasgow Photon Tagging Spectrometer to tag the photon energy with a resolution of ~4 MeV. The photons were incident on a liquid hydrogen target, and the reaction products were detected using the Crystal Ball and TAPS detectors. The beam-recoil polarisation observable Cx, which describes the fraction of circular polarisation transferred from the photon beam to the recoiling nucleon, was measured in the reactions γp→pπ0 and γp→pη from data taken in September-October 2008. The results for π0 production give a significant expansion of the world data set and are shown to be consistent with the few previous measurements taken at Jefferson Lab, USA, while the results for the η channel are a world first. The observed values for Cx are compared to the current solutions from the two leading partial wave analyses, SAID and MAID, with wide angular coverage up to a photon beam energy of 1400 MeV. Significant discrepancies in the prediction of Cx can be resolved by the new data.

The resonance spectrum of the nucleon gives direct information on the dynamics and interactions of its constituents. This offers an important challenge to the theoretical models of nucleon structure, including the emerging Lattice QCD predictions, conformal field theories and more phenomenological, QCD-based approaches. Although the various models predict different features for the excitation spectra, the experimental information is currently of too poor quality to differentiate between these models. Pion photoproduction from the nucleon is a powerful probe of the spectrum as most resonances are expected to couple to the pion decay channel. However, cross-sections alone are not sensitive enough to allow identification of the underlying excitation spectrum, as the resonances have energy widths larger than their separations. A major world effort is underway to additionally measure polarisation observables in the production process. For a model-independent analysis a “complete” set of single- and doublepolarisation observables needs to be measured in experiments involving polarised beams, targets and a means of determining recoil nucleon polarisation. In particular, the beam asymmetry is a critical observable for the constraint of partial wave analyses (PWA) used to extract the nucleon excitation spectrum from the data. Almost all of the available world data on the beam asymmetry has been taken on the proton, with the neutron dataset sparse, containing only three experiments at fixed angles and in a limited photon energy range. The lack of extensive data on the neutron is a major deficiency, as different resonances have very different electromagnetic couplings to the proton and neutron. As a result, the data from the two targets will have very different relative contributions from, and sensitivities to, the spectrum of nucleon resonances. Moreover, neutron data is essential for the separation of the isoscalar and isovector components of the reaction amplitudes. This thesis presents a very high statistics measurement of the photon beam asymmetry on the neutron with close-to-complete angular coverage and a wide range of invariant mass (1610 – 2320 MeV) extending over the third resonance region, where the excitation spectrum is particularly ill defined. The experiment was conducted at the Thomas Jefferson National Accelerator Facility (JLab) using a tagged, linearly polarised photon beam, a liquid deuterium target and the CEBAF Large Acceptance Spectrometer (CLAS). The quality and quantity of the data has allowed an invariantmass resolution of 10 MeV and an angular resolution of 0.1 in the cosine of the centre-of-mass pion production angle, θ. Good agreement is evident in the regions where there is kinematic overlap with sparse previous data. Comparison of the new data is made with the two main partial wave analyses, SAID andMAID. Significant discrepancy is observed at backward θ with SAID (across most of the energy range) and MAID (up to ∼ 1750 MeV) and also below ∼ 35◦ in θ with both analyses. This extensive new dataset will help significantly to constrain partial wave analyses and will be a crucial part of the current world effort to use meson photoproduction to tackle long-standing uncertainties in the fundamental excitation spectrum of the nucleon. As a first step towards this the refitting of the SAID partial wave analysis incorporating the new data was carried out and shows very significant changes in the properties of the magnetic P11, P13, D13, D35, F15, G17 and G19 partial waves.

Uma simulação baseada em métodos Monte Carlo foi criada com o intuito de avaliar a potencialidade da utilização do espalhamento Compton em altas energias para a obtenção de medidas absolutas e de alta precisão da energia de fótons marcados. Esse método se baseia em medidas angulares dos produtos desse espalhamento para reconstruir a energia dos fótons incidentes, utilizando a cinemática do espalhamento Compton em aproximação de impulso. A simulação inclui vários efeitos relevantes à medida, como espalhamento múltiplo de elétrons, momento interno dos elétrons nos átomos do alvo, resolução do detetor e vários parâmetros geométricos do arranjo experimental. Através da simulação de um experimento que utiliza esse método para a calibração em energia de um feixe de fótons marcados, foi possível identificar duas fontes de erros sistemáticos. Métodos de análise que minimiza um desse erros sistemáticos foram desenvolvidos, bem como métodos para a criação de correções para as medidas de energia. Verificou-se que, pelo menos no arranjo experimental estudado, é possível obter medidas da energia dos fótons incidentes com precisão da ordem de 0.07%. / A simulation based on Monte Carlo methods was created in order to evaluate the potentiality of using Compton scattering at high energies to obtain high precision absolute measurements of tagged photon energies. This method is based on angular measurements of the scattering products to reconstruct the incident photon energy using the kinematics of Compton scattering in impulse approximation. The simulation includes several effects that are relevant to the measurement, such as electron multiple scattering, internal momentum of the electrons in the atoms of the target, detector resolution and several geometrical parameters of the experimental setup. Through simulation of an experiment that uses this method for energy calibration of a tagged photon beam, it was possible to identify two sources of systematic errors. Analysis methods that minimize one of these systematic errors were developed, as well as methods for the creation of corrections to the energy measurements. Our results show that, at least in the studied experimental setup, it is possible to obtain energy measurements with a precision in the order of 0.07%.

Uma simulação baseada em métodos Monte Carlo foi criada com o intuito de avaliar a potencialidade da utilização do espalhamento Compton em altas energias para a obtenção de medidas absolutas e de alta precisão da energia de fótons marcados. Esse método se baseia em medidas angulares dos produtos desse espalhamento para reconstruir a energia dos fótons incidentes, utilizando a cinemática do espalhamento Compton em aproximação de impulso. A simulação inclui vários efeitos relevantes à medida, como espalhamento múltiplo de elétrons, momento interno dos elétrons nos átomos do alvo, resolução do detetor e vários parâmetros geométricos do arranjo experimental. Através da simulação de um experimento que utiliza esse método para a calibração em energia de um feixe de fótons marcados, foi possível identificar duas fontes de erros sistemáticos. Métodos de análise que minimiza um desse erros sistemáticos foram desenvolvidos, bem como métodos para a criação de correções para as medidas de energia. Verificou-se que, pelo menos no arranjo experimental estudado, é possível obter medidas da energia dos fótons incidentes com precisão da ordem de 0.07%. / A simulation based on Monte Carlo methods was created in order to evaluate the potentiality of using Compton scattering at high energies to obtain high precision absolute measurements of tagged photon energies. This method is based on angular measurements of the scattering products to reconstruct the incident photon energy using the kinematics of Compton scattering in impulse approximation. The simulation includes several effects that are relevant to the measurement, such as electron multiple scattering, internal momentum of the electrons in the atoms of the target, detector resolution and several geometrical parameters of the experimental setup. Through simulation of an experiment that uses this method for energy calibration of a tagged photon beam, it was possible to identify two sources of systematic errors. Analysis methods that minimize one of these systematic errors were developed, as well as methods for the creation of corrections to the energy measurements. Our results show that, at least in the studied experimental setup, it is possible to obtain energy measurements with a precision in the order of 0.07%.

The Compact Muon Solenoid (CMS) Experiment operates at the Large Hadron Collider (LHC) which is the highest energy particle accelerator in the world. CMS is a general purpose detector designed to investigate a wide range of physics, including the search for the Higgs boson. The measurement of photon production in the CMS experiment is crucial since it represents an irreducible background for many new physics searches, such as decay of Higgs to two photon, supersymmetry and extra-dimensions. The study of beam halo contamination is important for the correct measurement of photon production. This thesis presents a way to identify and remove this contamination by using the timing and the shower shape of the photons.

Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 113-119). Also available in electronic format on the Internet.

京都大学 / 0048 / 新制・論文博士 / 博士(理学) / 乙第13217号 / 論理博第1562号 / 新制||理||1638(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 教授 鶴 剛, 准教授 成木 恵 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DFAM

For more than 50 years attening filters have been inserted into the beam path oflinacs to produce a uniform energy fluence distribution of the photon beam and make it suitable for clinical use. Recently, linacs without flattening fifilter (Flattening FilterFree - FFF) are increasingly used in radiotherapy because of its benefifits, e.g. high dose rate (2000 MU/min), reduced scattered and leakage radiation. Hypofractionated radiotherapy is interested in the high dose rate of FFF beams to shorten the treatment delivery time (TDT) especially the FFF beams have acceptable flatness at small fifieldsizes. Radiotherapy techniques that deliver intensity-modulated beams (IMBs), e.g.Tomotherapy, intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), deal with the non-uniformity of the FFF beam profifile and produce homogeneous dose to the target as FF beams do. Siemens modified the Artiste linac in order to enable photon beam delivery with and without a flattening fifilter. The VMAT version developed by Siemens for Artiste linacs as a novel radiation technique is a modulated arc therapy (mARC). mARC technique is available with single, double and multiple complete or partial arcs. The aims of the current study were the determination of the main characteristics of 7 MV and 11 MV FFF photon beams in comparison with their corresponding 6 MV and 10 MV FF photon beams from Artiste digital linacs. Furthermore, IMRT planning comparisons using FF and FFF photon beams were performed using an Oncentra planning system. The performance of various mARC techniques were estimated and compared with Step and Shoot (S&S) IMRT by using a RayStation planning system. The mARC plans created by FF and FFF beams were evaluated to know which technique is the best. All the treatment plans were created for simple and complex shaped target volumes. The treatment plans are compared using two parameters - plan quality and treatment effi ciency. In addition to the planning study, the plan quality assurance of IMRT and mARC plans were performed using two difffferent volumetric quality assurance devices, Delta4 and Octavius 4D. Removal of the flattening fifilter causes changes in the dosimetric features of photon beams. IMRT plans with and without flattening fifilter were clinically acceptable where both plans have similar quality. In comparison with IMRT-FF, IMRT-FFF plansrequire more MUs and for some clinical cases require longer TDT. mARC technique can deliver dose distributions that are comparable to S&S-IMRT and could be an alternative with a potential to improve the effi ciency of the IMRT treatment delivery.:Abstract Abbreviation list 1 Introduction 2 Theory 2.1 Linac head configuration 2.2 Flattening fifilter disadvantages 2.3 Flattening fifilter free beams 2.4 Intensity modulated radiation therapy 2.5 Multi leaf collimator 2.6 Step and shoot IMRT 2.7 Dynamic delivery 2.8 Intensity modulated arc therapy 2.9 Modulated arc therapy 2.10 Verification of IMRT and mARC treatment plans 3 Materials and Methods 3.1 Materials 3.1.1 Linear accelerator 3.1.2 Dosimetric tools 3.1.3 Dosimetric verification systems 3.1.4 Treatment planning systems 3.2 Methods 3.2.1 Dosimetric parameters of FF and FFF beams 3.2.2 Comparison of IMRT-FF and IMRT-FFF 3.2.3 mARC planning study 3.2.4 Planning comparison parameters 3.2.5 Dosimetric verification 4 Results 4.1 Dosimetric characteristics of FF and FFF beams 4.1.1 Dose rate 4.1.2 Dose profile 4.1.3 Depth dose curve 4.1.4 Dose in buildup region 4.2 Comparison of IMRT-FF and IMRT-FFF 4.2.1 Plan quality 4.2.2Treatment e ciency 4.3 mARC 4.3.1 Final gantry spacing (F.G.S) 4.3.2 mARC and IMRT 4.3.3 Comparison of mARC 10 MV FF and 11 MV FFF plans 4.3.4 Plan verifications 5 Discussion 5.1 Dosimetric parameters of FF and FFF beams 5.2 IMRT-FF and IMRT-FFF 5.3 mARC Summary Bibliography Selbstandigkeitserklarung Curriculum Vitae Acknowledgement

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20248号 / 医博第4207号 / 新制||医||1020(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 鈴木 実, 教授 別所 和久, 教授 大森 孝一 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM