No description available.

The results presented in this thesis are from the preliminary data on a K P formation experiment. The experiment was carried out at the Rutherford Laboratory using the British National Hydrogen bubble chamber with a Track Sensitive Target (T.S.T.) to afford gamma-ray detection. The final states selected for the analysis are Λºπº, ϵºπº and Kºn at incident momenta between 200 and 500 MeV(_c). The T S T technique employed in this experiment is discussed in detail, in particular its limitations and how they should be handled are described. The cross-sections for Λº + neutrals, Λºπ(^+)π(^-) and Kºn channels are obtained in 20 MeV (_c) momentum intervals and the presence of the Λ (1520) is quite clear. The kaon flux is determined by using the observed tau-decays. The data is divided into 6 intervals of incident momentum between 250 and 500 MeV(_c) and fits are made to the distribution of missing mass squared to the A -hyperon, the production angular distribution and the polarisation of the A . These fits gave the Legendre expansion coefficients describing the angular distributions and the polarisations for the Λºπº and ϵºπº final states. The results are in good agreement with the previous data. Finally events fitted as Λºπº and ϵºπº hypotheses with one associated gamma-ray are chosen. Here the gamma-ray is used to resolve the Λº/ϵº ambiguity. The observed production angular distributions for these events are compared with the results from the fit above using Λº and ϵº events without gamma-rays. Also, the decay proton angular distribution of the fitted ϵºπº events is compared with the results from the fit. There is a good consistency between the two results and that of the previous data.

No description available.

This thesis investigated the design decisions and associated optimisation methods of a 1.3 GHz Multiple Beam Klystron (MBK) for use in the Compact Linear Collider (CLIC). In this regard refinements have been made both to the MBK design, and investigation and optimisation methods used. The high desired efficiency of 80% requires low perveance beams, to achieve the specification output power 20 beams are needed. The choice of cavity used in the interaction structure of a klystron has a large impact on its size and efficiency. To optimise this a number of possible cavity designs were produced and compared to confirm selection of the most appropriate. The fundamental mode (TM0, 1, 0) coaxial cavity was selected due to its superior R/Q of 130-210 W and suitability as a 2nd harmonic cavity. Although the dipole mode proved to be close in frequency to the operating mode (within ~ 50 MHz), raising concerns of stability issues in an MBK. A novel model was developed using standard wake field theory to investigate the effects of this mode the klystron’s stability. A strategy for shifting this mode using a coupled shifting gap was proposed and achieves a shift of 125 MHz, although the models findings suggest it is not a significant problem. Existing methods of calculating dipole and higher order modes proved time consuming thus impeded a fully investigation of stability issues. An extended method of moments model allows efficient calculation of monopole and higher order modes. The model’s basis functions are altered to represent a range of TM and TE modes with azimuthal variation, allowing their rapid and accurate calculation. Optimising the klystron interaction structure by hand to find a viable configuration revealed shortcomings in this standard approach, although the target efficiency was achieved. An algorithmic approach was deemed necessary to allow a full investigation within reasonable time limits. The field of evolutionary algorithms is presented and an evolutionary algorithm to automate the optimisation of klystron interaction structures was developed. A number of important related issues were dealt with and suitable interaction structures (optimised for efficiency, bandwidth, length and electron exit velocity) produced. Finally a design was proposed for both the input and output couplers which is inspired by a coupler used in a gyrotron. Unconventionally, the latter exits the tube axially avoiding the focusing solenoid, but excessive heating may preclude its use.

The hard photoproduction of jets has been studied using the ZEUS detector at HERA. The data were collected during the 1996-1997 e+p running period and correspond to an integrated luminosity of 38.6 pb-1. Events were selected with a photon-proton centre-of-mass energy in the range 134 W7P 277 GeV with photon virtualities of Q2 1 GeV2. Jets were defined using the longitudinally invariant k algorithm in the inclusive mode. Cross sections for the photoproduction of four high transverse energy jets have been measured. This is the highest order process in QCD to have been studied at HERA to date. Two kinematic regions have been defined: the inclusive and the high mass samples. The high mass sample contains only events with a four jet invariant mass satisfying m.;j 50 GeV. The data axe compared to parton shower models which resum leading logarithms to produce multi-parton final states. The inclusive distributions are found to be very sensitive to the underlying event model. Models with no simulation of the underlying event are unable to describe the shape of the distributions. Inclusion of only a soft underlying event is also disfavoured. However, the description of the data is significantly improved by inclusion of multi-parton interactions, which introduces a hard, partonic scattering component to the underlying event. The high mass cross sections are well described by the parton shower models and are relatively insensitive to the underlying event model and, consequently, are considered suitable for comparison with fixed order perturbative QCD calculations when they become available. The rate of four jet photoproduction, relative to that of three jet, shows an excess over the predictions of models which use only initial- and final-state QCD radiation to produce multi-parton final states. The data can be described by models including multi- parton interactions, which provides an additional mechanism for the production of four jets. The data from this analysis have also been used to provide constraints on the parton shower model parameters. Cross sections for the photoproduction of two jets separated by a large region in rapidity have been measured. Rapidity gap events are defined in terms of the energy flow in the region between the two highest transverse energy jets. Gap fractions, defined as the ratio of the two jet gap cross sections to the two jet inclusive cross sections, have also been measured. An excess of events with a rapidity gap, over that expected from standard QCD, is observed. This can be interpreted as evidence for the exchange of a strongly interacting colour singlet object. The data are well described by the leading logarithmic approximation BFKL pomeron with a choice of c.;re' = af271' = 0.18 and UJQ = 0.48. Taking into account the constraints imposed on the underlying event model from the multi-jets analysis, an estimate of S = 65 - 70% has been estimated for the gap survival probability.

The LHCb experiment is a high energy physics detector at the Large Hadron Collider. The experiment has been designed and built to search for new physics in the b hadron sector. This thesis discusses a contribution to the detector construction and preparatory studies for a rare decay analysis. Quality assurance of the silicon modules of LHCb vertex detector One of the critical components of the LHCb experiment is the silicon vertex locator (VELO), which is used to measure the decay distance of the $b$-hadrons and is a principal component of the tracking of the experiment. This thesis describes the quality assurance tests of the VELO silicon modules. A facility was designed to operate the VELO modules in vacuum and thermally stress the modules. To verify the suitability of the modules for the experiment a range of studies were performed including measurements of the silicon leakage current and the identification of bad channels through a noise analysis. A full set of 42 modules (and spares) suitable for use in the experiment were successfully tested. Analysis of the $B_d\rightarrow K^* \mu^{+}\mu^{-}$ decay The $B_d\rightarrow K^* \mu^{+}\mu^{-}$ decay is a flavour changing neutral current process which occurs only via loop diagrams. This is a rare process with a measured branching ratio of \\$\rm 1.10^{+0.29}_{-0.26} \times 10^{-6}$. The $B_d\rightarrow K^* \mu^{+}\mu^{-}$ rare decay is sensitive to new physics (NP) effects. Through the measurement of the so-called forward backward asymmetry distribution a clear signature of NP can be found in this channel. The estimated number of signal events expected per year in LHCb ($\rm 2 fb^-1$) was estimated to be $\rm 7.0\pm0.1\times 10^{3}$. The sensitivity to the zero point of the forward backward asymmetry was calculated as $\rm 0.4~GeV^{2}/c^{4}$, assuming the estimated annual yield. Degradation of the sensitivity due to background events was estimated to be $\rm \sim10-15\%$. Potential systematic effects due to acceptance and background mismeasurement are also presented. The results on the forward backward asymmetry were obtained using a non-parametric unbinned method.

We present results for the ∆I = 3/2 K → ππ decay amplitude computed using lattice quantum chromodynamics. The calculation is performed using 2 + 1 flavours of domain wall fermion and the Iwasaki gauge action modified by the dislocation suppressing determinant ratio, on a lattice volume of 32^3 × 64 × 32 at lattice spacing a^−1 = 1.364 GeV. The resulting valence pion mass is mπ = 142.11 MeV, and the kaon mass is mK = 505.5 MeV. A total of 146 configurations are analysed, giving ReA2 = 1.381(46)stat (258)syst × 10−8 GeV and ImA2 = −6.54(46)stat (120)syst × 10^−8 GeV. The experimental results for ReA0 and ReA2 and ǫ′/ǫ are combined with this lattice result for ImA2 to give ImA0 /ReA0 = −1.61(28) × 10^−4. We also present results from a second calculation where both the ∆I = 1/2 and ∆I = 3/2 K → ππ decay amplitudes are calculated. This calculation is performed using 2 + 1 flavours of domain wall fermions with the Iwasaki gauge action and a lattice size of 16^3 × 32 × 16. Since the evaluation of A0 is technically challenging, this first ever determination of A0 is performed at threshold with a heavy pion mass of mπ ∼ 420 MeV. The results are Re(A0) = 3.80(82) × 10^−7 GeV and Im(A0) = −2.5(2.2) × 10^−11 GeV.

No description available.

The Compact Linear Collider (CUC) is a proposed electron-positron collider with a centre- of-mass energy of 0.5 to 5 TeV, optimised for a nominal centre-of-mass energy of 3 TeV, at high luminosities exceeding 1034 cm-2s-J. The high beam charges in the CUC beams make classical techniques for measuring the transverse beam size such as optical transition radiation (OTR) screens or wire scanners very difficult, which necessitates the use of non-invasive beam- size monitors. The laser-wire is a system that meets these requirements; it uses inverse Compton scattering to determine transverse beam-sizes by scanning a laser beam across the electron beam. This thesis describes how such a laser-wire system was installed and operated at PETRA-III at DESY, which uses an automated mirror to scan a Q-switched laser pulse across the electron beam and is developed from the system previously operated at PETRA-II. The measurements of key performance parameters are described and used in determining the emittance of the PETRA-III beam. The thesis includes a detailed investigation of the laser .' system as well as the collision measurements. Furthermore, simulations were carried out to design a similar system for the proposed transfer line of the CUC Drive-Beam and the necessary baseline characteristics of such a system are described.

T2K est une expérience de neutrinos à longue ligne de base à base d'accélérateurs au Japon. Le but principal de l'expérience T2K est la recherche d'une violation de la PC dans le secteur du lepton en mesurant l'apparence (anti)neutrino des électrons dans un faisceau muon (anti)neutrino. Le flux (anti) neutrino initial est produit par les désintégrations des hadrons qui proviennent des interactions et des ré-interactions d'un faisceau de protons de 30 GeV avec une cible en graphite de 90 cm de long. La connaissance du flux de neutrinos T2K est limitée en raison des grandes incertitudes liées à la production de hadrons. Une série de mesures de production d'hadrons a été effectuée pour résoudre ce problème, dans l'expérience NA61/SHINE au CERN. Les mesures ont été effectuées avec un faisceau de protons et deux types de cibles : une cible en graphite mince et une réplique de la cible T2K. Les travaux présentés dans cette thèse se concentrent sur les données cibles de la réplique T2K prises en 2010 et sur le développement du logiciel d'analyse et d'étalonnage. Le but de ces mesures est de contraindre complètement la production de π+, π+, π-, K+, K+, K- et p provenant de la surface cible en mesurant les rendements différentiels en hadrons dans les cellules du momentum de particules sortant (p), l'angle polaire (θ) et la position longitudinale sur la surface cible (z). Cela permettra de réduire les incertitudes du flux de neutrinos T2K d'environ 10 % à moins de 5 %. Les prédictions de Fluka2011.2c.5 Les listes de physique Monte Carlo, NuBeam et QGSP_BERT de Geant4.10.03 ont été comparées aux données et il a été constaté que Fluka2011.c2.5 donne la meilleure prévision. / T2K is an accelerator-based long-baseline neutrino experiment in Japan. The main goal of the T2K experiment is a search for CP violation in the lepton sector by measuring electron (anti) neutrino appearance in a muon (anti)neutrino beam. Initial (anti) neutrino flux is produced in decays of hadrons which originate from the interactions and the re-interactions of a 30 GeV proton beam with a 90 cm long graphite target. Knowledge of the T2K neutrino flux is limited due to large hadron production uncertainties. A series of hadron production measurements were done to solve this problem, in the NA61/SHINE experiment at CERN. Measurements were performed with a proton beam and two target types: a thin graphite target and a replica of the T2K target. Work presented in this thesis concentrates on the T2K replica target data taken in 2010 and the development of the analysis and calibration software. The aim of these measurements is to fully constrain production of π+ , π− , K+ , K− and p coming from the target surface by measuring differential hadron yields in the bins of outgoing particle momentum (p), polar angle (θ) and longitudinal position on the target surface (z). This will allow reduction of the T2K neutrino flux uncertainties from around 10% to below 5%. Predictions of Fluka2011.2c.5 Monte Carlo, NuBeam and QGSP_BERT physics lists from Geant4.10.03 have been compared to the data and it has been found that Fluka2011.c2.5 gives the best prediction.