Dissertations / Theses: 'Elementary Particles and High Energy Physics'

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Lemieux, François 1979. "Are inflationary predictions sensitive to very high energy physics?" Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80316.

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It was recently proposed that modifications to physics at trans-Planckian energies could lead to a non-adiabatic evolution of the scalar fluctuations responsible for the temperature anisotropy of the cosmological microwave background. If such a possibility was to be confirmed, it would provide us the first possibility to ever get experimental measurements of the physics near the Planck scale. This work investigates the physicality of such non-adiabatic evolutions, by avoiding the introduction of any exotic physics, by working well below the Planck scale. Simple 'hybrid-like' models of inflation composed of an inflaton field coupled to another heavy scalar will be used. It will be shown that small oscillations in the heavy scalar field can generate a non-adiabatic evolution of the inflationary vacuum leading to new features in the power spectrum that could eventually be observed. The naturalness of this non-adiabaticity is also studied, leading to a constraint about the maximum duration of inflation if these effects are to be big enough to ever be detectable.

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2

Towrie, Michael. "Multiphoton resonant ionisation : applications to high energy physics." Thesis, University of Glasgow, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280015.

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Allan, Anthony Robert. "Signatures of new particles at high energy colliders." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/7091/.

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We discuss the experimental signatures of new particles, predicted by the Standard Model and by super symmetry, in high energy proton-antiproton and, or, electron-positron colliders. A review of the theory of the Standard Model and of Supersymmetry, and a general discussion of collider physics are included. We review various Higgs boson production mechanisms, and consider one, Higgs boson production via Bremsstrahlung from electroweak gauge bosons, in detail. We find that the clearest signature is seen in the invariant mass distribution of the electron pair in the process ρρ → X (Z → He÷e־). However, the event rate is small, and, unless the Higgs boson can be identified from its decay products, such events may be misidentified as ordinary Z → e÷e־ events. We analyse UA1 jet-plus-large-missing-p┬ events in terms of a supersymmetric model with a light photino and with m≈ < m≈. If these events are due solely to scalar quark production, we find that, in our scenario, the scalar quarks must have a mass in the range 20 - 35 GeV, and the gluino mass must be greater than 0(60) GeV. We study the production of scalar electrons in e÷e־ collisions on and above the Z resonance. By calculating the cross-sections for e÷e־ → e÷eﻵﻵ־ we show that scalar electrons with mass above the beam energies (√s/2) can be identified. In particular, if a zino exists with mass m? < /s-m?. , then zino production and decay can give a contribution which dominates the ﻵ-exchange contributions. In this case the presence of both the ẽ and Ž may be revealed by a distinctive signature in the electron momentum distribution.

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Shao, Shu-Heng. "Supersymmetric Particles in Four Dimensions." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493285.

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In this dissertation we study supersymmetric particles in four spacetime dimensions and their relations to other physical observables. For a large class of four-dimensional N=2 systems, the supersymmetric particles are described by the ground states of certain quiver quantum mechanics in the low energy limit. We derive a localization formula for the index of quiver quantum mechanics with four supercharges. Our answer takes the form of a residue integral on the complexified Cartan subalgebra of the gauge group. The wall-crossing phenomenon appears as discontinuities in the value of the residue integral as the integration contour is varied. We then move on to study the ground states in the Kronecker model of quiver quantum mechanics. This is the simplest quiver with two gauge groups and bifundamental matter fields, and appears universally in four-dimensional N=2 systems. The ground state degeneracy may be written as a multi-dimensional contour integral, and the enumeration of poles can be simply phrased as counting bipartite trees. We solve this combinatorics problem, thereby obtaining exact formulas for the degeneracies of an infinite class of models. For large ranks, the ground state degeneracy is exponential with the slope being a modular function that we are able to compute at integral values of its argument. We also observe that the exponential of the slope is an algebraic number and determine its associated algebraic equation explicitly in several examples. The speed of growth of the degeneracies, together with various physical features of the bound states, suggests a dual string interpretation. In the last part of the dissertation, we conjecture a precise relationship between a limit of the superconformal index of four-dimensional N=2 field theories, which counts local operators, and the spectrum of BPS particles on the Coulomb branch. We verify this conjecture for the case of free field theories, N=2 QED, and SU(2) gauge theories coupled to matter. Assuming the validity of our proposal, we compute the superconformal index of all Argyres-Douglas theories. Our answers match expectations from the connection of Schur operators with two-dimensional chiral algebras.
Physics

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Patrick, Richard J. II. "The search for supersymmetry in particle physics." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527406.

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Experimental high energy physics (HEP) techniques are applied to accurate simulated collider data in search for existence or exclusion of supersymmetric (SUSY) particles. Supersymmetry is a leading candidate to resolve the hierarchy problem in particle physics as well as offer a stable dark matter candidate. Techniques and practices are explored and applied to the leptonic decay process production followed by and where is the proton, is the chargino, , are neutralinos and , are the standard model W and Higgs Bosons respectively. Signal yields are in general agreement with other researchers and ranged from 0.5 to 62.6 events. Reduction in the background to signal ratio is demonstrated through isolating the SUSY process and applying theoretical knowledge of the signal and associated dominant backgrounds. Results from this study establish procedures for future work with actual data, offer a benchmark for this specific leptonic decay process and may motivate variable selection and cut criteria choices in future analysis of similar signal processes.

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Feige, Ilya Eric Alexander. "Factorization and Precision Calculations in Particle Physics." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467340.

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We state and prove to all orders in perturbation theory a factorization theorem in Quantum Chromodynamics that concisely describes the separation of the physics associated with jet formation from that associated with the hard-scattering in high-energy particle collisions. We show how the factorization theorem, which provides an equality between amplitudes in gauge theories, can be readily applied to precision calculations of cross-sections. In the resulting factorized cross sections, the components relevant to jet production are universal and perturbatively calculable. Their renormalization group evolution can be used to sum large logarithms of scale ratios to all orders in perturbation theory, thus enabling quantitive predictions in the regime of disparate scales relevant to many important collider-physics observables. As an application, we calculate the observable 2-subjettiness at next-to-next-to-next-to-leading-logarithmic order for the decay of boosted heavy color-singlet particles such as Electroweak bosons. Our calculation is the first analytic calculation of a jet substructure observable.
Physics

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Glover, Edward William Nigel. "Studies of high energy pp collisions." Thesis, Durham University, 1985. http://etheses.dur.ac.uk/7113/.

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The Standard Model of particle physics is examined in the context of high energy proton-antiproton collider experiments. The large energies available offer the possibility of producing new particles which may then be observed via their decay. Heavy quark production is examined through the production of unlike-sign lepton pairs. Methods for isolating several dilepton production mechanisms are given, including an eu signal for the top quark. Moreover, ψ production is shown to serve as a particularly clean tag for the production of particles containing b quarks. The possibility of observing a fourth generation heavy lepton via W decay is investigated. The hadronic decay mode leads to a promising signature of large missing accompanied by two hadronic jets and has a very healthy event rate. The monojet events found by the UA1 experiment are reviewed. Various extensions of the Standard Model are examined as possible explanations of these events. The first interpretation involves the production of SUSY particles. These are found to be compatible with the data if two squarks exist with mass 0(30GeV) and the gluino has mass > 0(60GeV). Secondly, interpretations based on four point effective interactions of the form qqZg are investigated, and are shown to be unable to account for the observed monojet rate. Finally, the production and decay of new heavy states (for example excited quarks) could account for the monojet data, but are found to predict large numbers of W + jet and γ + jet events which have not been seen.

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Bertrand, Martine 1976. "Photon production in high energy heavy ion collisions." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31196.

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The production of photons in the energy range of 0 to 3 GeV is discussed as a signature of the creation of a quark-gluon plasma in ultrarelativistic nuclear collisions. However, they are also created in the hadronic phase. Therefore I investigate the role of the pirho → pigamma and pio → pigamma reactions in the photon emission from hot hadronic matter, and I compare their respective importance. These reactions are known to be the leading contributions. For this purpose I use diverse effective chiral Lagrangians that are in accord with known empirical properties of strong interaction. Then I discuss the relevance of my work to heavy ion collisions.

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Kiourkos, Socrates. "Development of Microstrip Gas Chambers for high energy physics experiments." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262391.

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Shuhmaher, Natalia. "Aspects of cosmology from physics beyond the standard model." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18460.

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The interface of Cosmology and High Energy physics is a forefront area of research which is constantly undergoing development. This thesis makes various contributions to this endeavor. String-inspired cosmology is the subject of the first part of the thesis, where we propose both a new inflationary and a new alternative cosmological model. The second part of the thesis concentrates on the problems of integrating cosmology with particle physics beyond the Standard Model. Inspired by new opportunities due to stringy degrees of freedom, we propose a non-inflationary resolution of the entropy and horizon problems. In this string-inspired scenario, 'our' dimensions expand while the extra dimensions first expand and then contract, before eventually stabilizing. The equation of state of the bulk matter (which consists of branes) is negative. Hence, there is a net gain in the total energy of the universe during the pre-stabilization phase. At the end of this phase, the energy stored in the branes is converted into radiation. The result is a large and dense 3-dimensional universe. Making use of similar ideas, we propose a not-fine-tuned model of brane inflation. In this scenario the brane separation, playing the role of the inflaton, is the same as the overall volume modulus. The bulk matter provides an initial expansion phase which drives the inflaton up its potential, so that the conditions for inflation are realized. The specific choice of the inflationary potential nicely fits the cosmological observations. Another aspect of this research concentrates on the cosmological moduli problem: namely, the existence of weakly coupled particles those decay is late enough to interfere with Big Bang Nucleosynthesis. As a solution, we suggest parametric and tachyonic resonances to shorten the decay time. Even heavy moduli are dangerous for cosmology if they cause the overproduction of gravitinos. We find that tachyonic decay channels help to transfer most of the energy of thes
L'interface entre la Cosmologie et la Physique des hautes énergies est un sujet de recherche d'avant-plan en constant développement. La cosmologie inspirée par la théorie des cordes est le sujet de la première partie de cette thèse, dans laquelle nous proposons d'une part un nouveau mécanisme pour l'inflation et d'autre part une nouvelle alternative de modèle cosmologique. Dans la seconde partie nous nous concentrons sur les problèmes reliés à l'intégration de la cosmologie dans un modèle de physique des particules au-delà du Modèle Standard. Motivés par les nouvelles possibilités venant des degrés de liberté de la théorie des cordes, nous proposons une résolution non-inflationiste aux problèmes d'entropie et d'horizon. Selon notre scenario fondé sur la théorie des cordes, les trois dimensions spatiales habituelles ainsi que les dimensions supplémentaires s'étendent, mais ces dernières se contractent eventuellement avant de se stabiliser. L'équation d'état de la matière du bulk, qui consiste de branes, est négative. Il y a donc un net gain dans l'énégie totale de l'univers durant la phase de pré-stabilisation. A la fin de cette phase, l'énergie stockée dans les branes est convertie en radiation. Le résultat est un univers tri-dimensionel large et dense. En utilisant des idées similaires, nous proposons un modèle d'inflation qui ne requiert pas d'ajustements fins. Dans ce scénario, la séparation entre les branes, qui joue le rôle de l'inflaton, est la même que le module du volume global. La matière du bulk fournit une phase d'expansion initiale qui pousse l'inflaton vers le haut de son potentiel, réalisant ainsi les conditions pour l'inflation. Le choix spécifique du potentiel de l'inflaton est en accord avec observations cosmologiques. Un autre aspect de ma these adresse le problème cosmologique des champs de module: c'est-à-dire l'existence de particules faiblement couplées dont la désintégration a li

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11

Gagnon, Olivier. "Limits on Lorentz non-invariance from high energy cosmic rays." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82235.

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We put strong constraints on Lorentz violation by studying the inner structure of highly energetic protons. Our work is in direct continuation of previous analysis based on dimensions 4, 5 and 6 Lorentz violating operators. Our original contribution is due to the study of the inner structure of hadrons and their relation with Lorentz violating operators. The strength of the constraints arising from this new analysis should discourage us to propose new general theories that are Lorentz violating.

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Punch, Sean M. "Radiative mass generation from new Physics in the Quark sector." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56763.

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A model is presented which consists of a dynamical scheme for reproducing the mass hierarchies observed in the quark sector. This is accomplished through new physics beyond the Standard Model, and does not rely upon the Higgs mechanism. By introducing a heavy fermion which couples to the quarks via the emission and reabsorption of a new boson, initially massless quarks are given their masses in a purely radiative fashion. The differences between up and down sector masses appear naturally as a result of generating the down mass matrix from corrections to the up mass matrix: accomplished via an anomalous flavour-changing coupling to the weak sector. Multipole type form-factors are inserted at each coupling, and introduce parameters which are varied to produce numerical fits to the quark masses, mixing angles and CP-violation parameter. Several extensions to the model are proposed and discussed.

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Kamal, Basim. "Higher order QCD corrections to processes with polarized particles." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29058.

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QCD higher order corrections (HOC) to three processes are considered: (i) Direct photon production in longitudinally polarized hadron-hadron collisions with numerical applications to proton-proton collisions; (ii) lepton-pair production in transversely polarized hadron-hadron collisions with numerical applications to proton-proton collisions; (iii) heavy quark pair production by polarized and unpolarized photons. The HOC to all three processes are found to be significant. Processes (i) and (ii) are shown to be sensitive probes of the proton's polarized gluon distribution and the transversity distributions, respectively. The asymmetries are found to exhibit perturbative stability. Process (iii) is considered as a background to $ gamma gamma rightarrow H sp* rightarrow b =b$ (standard model). As well, top-quark production not too far above threshold is considered.

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Roussel, Harold. "Solution generating techniques in low energy effective string theory." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ37018.pdf.

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15

Wang, Chao. "A model study of the dynamics of dark energy." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106572.

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Observational facts indicate that the expansion of the universe is accelerating, rather than decelerating, because 73% of the total energy density of the universe is a "dark energy" with strong negative pressure, ω < −1/3. In this thesis, we introduce a dynamical dark energy model with dilatational symmetry, which contains two scalar ﬁelds coupled to gravity. Because of the dilatational symmetry, there is no cosmological constant Λ in the Lagrangian, and, instead, two scalar ﬁelds generate the dark energy, evolving slowly in time. At early times, the system is in the slow roll regime, corresponding to Higgs inﬂation due to the Higgs ﬁeld. At late times, the dynamical dark energy dominates the universe and eventually behaves just like the cosmological constant, and the universe becomes exponentially expanding with the scale factor a(t) ∝ exp{Ht}. The numerical results from solving the dynamic equations of the system agree well with the observational facts, which indicates that our model gives a good description of the universe. At the end of the thesis, we consider the one-loop corrections to our model, and show that they do not alter the classical results in any signiﬁcant way.
Les observations actuelles de l'expansion de l'univers indiquent une accéleration decette expansion due à 'l'énergie sombre', qui compte pour 73% de la densité d'énergie totalle de l'univers et qui se comporte comme un ﬂuide avec une pression négative, ω < −1/3. Cette thèse présente un modèle dynamique d'énergie sombre invariant sous une symétrie de dilatation comprenant deux champs scalaires couplés à la gravitation. La constante cosmologique n'est pas présente dans ce modèle, de par la symétrie de dilatation; les champs scalaires génèrent une énergie sombre évoluant dans le temps. Dans l'univers primordial, le système se situe dans le régime d'évolution lente correspondant à l'inﬂation cosmolgique due au champ de Higgs. L'énergie sombre dynamique agit ultérieurement sur l'évolution de l'univers comme une constante cosmologique; le facteur d'échelle de l'univers accroit de manière exponentielle a(t) ∝ eHt. Les simulations numériques concordent très bien avec les observations actuelles. Les perturbations quantiques de premier ordre sont ensuite calculées, et justiﬁent la validité des résultats obtenus de manière classique.

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Colón, Samuel Santana. "Phenomenological model combining flavor symmetry violation and lepton number violation in neutrino physics." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3334993.

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Hogue, Caroline. "Computer modelling of the motion of granular particles." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239032.

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Wambach, Achim. "Consistent application of quark models to heavy flavour physics." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386750.

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19

Zioulas, George. "Pizero and direct photon production at high transverse momenta." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74622.

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The inclusive pizero and direct photon productions by 300 GeV/c $ pi sp-$ and $ pi sp+$ beams on a lithium target, were measured using the E705 spectrometer at Fermilab. The cross sections were determined by analyzing a fraction (20%) of the data recorded by the experiment during the 1987-1988 running period. The photons were measured by a high resolution electromagnetic calorimeter which consisted of scintillation and lead glass blocks. A fast trigger was designed and implemented to select events with high transverse energy depositions in the calorimeter.
The invariant cross sections are presented as a function of the transverse momentum and the Feynman-x in the range between 4 to 7 GeV/c and $-$0.25 and 0.35 respectively. The results are compared to the measurements made by other experiments and to theoretical predictions within the framework of Quantum ChromoDynamics.

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Kaziewicz, Philip Bernard. "Energy flows in deep inelastic scattering at HERA." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244503.

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Marini, Alexander L. "The quark and gluon damping rates in high-temperature QCD /." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61194.

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The dominant term in the damping rate for quarks and transverse gluons at high momentum (p $ gg$ gT) is calculated within the framework of perturbative QCD at finite temperature. It is shown that the damping rate, $ gamma$, takes the form $ gamma$ = cg$ sp2$T log(1/g) with c = N/4$ pi$ for transverse gluons and c = (N$ sp2$-1)/(8$ pi$N) for quarks where N is the number of colours, g is the coupling constant, and T is the temperature. The sign and the gauge invariance of $ gamma$ are easily verifiable due to the simplicity of the argument. This result agrees with the more complicated (unpublished) calculations of Pisarski et al. but disagrees with those of Lebedev and Smilga.

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Curley, D. P. "Non-abelian monopoles and their interactions with charged particles." Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356566.

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Ochs, Andreas H. "Dijet photoproduction at high transverse energies with the ZEUS detector at HERA." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83085.

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Photoproduction events in ep collisions with photon virtuality Q2, the negative squared four-momentum of the exchanged photon, less than 1 GeV2, and at least two jets of high transverse energy have been studied in the photon and proton center-of-mass range Wgp of 134 < Wgp < 277 GeV with the ZEUS detector at HERA. The data sample was collected during the 1996 and 1997 running periods with an integrated luminosity of 38.7 pb-1 allowing for a precise measurement of differential cross sections in a kinematic regime unreachable for experiments at current e+e- colliders. For the determination of these differential cross sections, both jets were required to have a transverse energy larger than 11 GeV with at least one having more than 14 GeV. Differential hadron cross sections were extracted for these dijet events using separate resolved and direct enhanced subsamples. The cross sections have been compared to NLO QCD calculations using several different parametrisations of the photon structure functions within these calculations. The achieved sensitivity of the data at the photon structure functions allows to test the validity of the used parametrisations of the photon structure functions. This test shows the need for improvements of those parametrisations in the kinematical range under investigation. The extracted data at low xOBSg constrains the parton densities in the photon which can be exploited in future parametrisations of the photonic parton densities.

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Sato, Yoichi. "Electron-proton dynamics for long proton bunches in high intensity proton rings." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3243796.

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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007.
Title from PDF t.p. (viewed Nov. 18, 2008). Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 7138. Adviser: Shyh-Yuan Lee.

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Siddles, R. M. "Laser fluorescence studies of energy transfer at low temperatures." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280003.

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Burrows, Philip Nicholas. "QCD processes and hadron production in high energy e+e- annihilation." Thesis, University of Oxford, 1988. https://ora.ox.ac.uk/objects/uuid:8d5c0284-48a7-429d-9c7a-28a033bb1e8c.

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A study is presented of general features of the reaction e⁺e^-â hadrons. The data are interpreted in terms of current models of the underlying QCD and hadronisation processes. These models are outlined in detail and their predictions are compared with most of the available experimental data collected between 12.0 and 46.8 GeV mean centre of mass energies. The model arbitrary parameters were optimised to give a generally good description of the global properties of the large hadronic event sample accumulated by the TASSO detector at 35 GeV: The Lund O(Î±²_s) model describes properties in the event plane very well, but is deficient in the properties transverse to this plane. The Webber LLA model gives a good description of the transverse observables, but overestimates those quantities in the plane. The Lund LLA + O(Î±²_s) model provides a good representation of the transverse properties but underestimates some quantities in the plane, though the discrepancy is much smaller than for the LLA model. The evolution of the observables as a function of c.m. energy between 12.0 and 41.5 GeV is generally well described, the Lund LLA + O(Î±²_s) model representing the data best. It is concluded that this model is successful in reproducing accurately most features of the data because it includes QCD calculations of both hard and multiple soft gluon emission processes. The model predictions are extended up to W = 200 GeV, where the two parton cascade models give similar predictions of the event properties which differ significantly from those of the 0(Î±²_s) model. Top quark production is simulated at W = 200 GeV for a top mass of 60 GeV/c² and the distributions of thrust, aplanarity, PT_in,PT_out and rapidity are found to be most sensitive to its presence. The data at 35 GeV are also analysed in terms of explicit multijet final states and compared with the QCD model calculations. The 0(α²_s ) model is unable to account for the observed rates of 4- and 5- jets per event, though it reproduces the 2- and 3- jet rates reasonably well. The LLA model gives a better description of the rates of â¥ 4-jets but gives too few 3-, and too many 2-jet events. The LLA + O(Î±²_s) model is able to reproduce all jet rates well. All the models describe the trend of the evolution of the jet rates between <âs> = 14 and 43.8 GeV. It is shown that the rate of 3-jet events seen in the data decreases as s increases in a manner consistent with the Q² dependence of Î±_s as predicted by QCD.

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Hickman, Malcolm Timothy. "Inclusive photo- nad hadro- production of eta mesons at high energy." Thesis, Lancaster University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306556.

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Summers, David John. "Phenomenology of the Standard Model, and beyond, at high-energy colliders." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5619/.

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I review planned searches for the so far unobserved Higgs boson of the Standard Model of High Energy Physics. In particular a light 'intermediate' mass Higgs with mass in the range 80 GeV ≤ M(_H) ≤130 GeV will be hard to detect. I suggest several methods at planned future high energy particle colliders for observing this Higgs boson. At LEP I we have reasonable numbers of Higgs produced in association with a Z boson up to the limit imposed by phase space M(_H) ˂ √s - 100 GeV. Unfortunately if the Higgs is degenerate in mass with the Z boson we have large numbers of background events from double Z production. I investigate possible methods round this background. Firstly in polarizing the initial e+e- beams, and secondly in studying the differing topologies of the ZH signal, and ZZ background events. Moving on to the hadron super colliders the LHC and the SSC. These colliders typically produce very clean signals for 'heavy' Higgs. However for a light "'intermediate* mass Higgs all Higgs decays are either dominated by huge QCD backgrounds; or put very strong constraints upon our experimental apparatus. I investigate the signals and backgrounds for an alternative approach where rather than looking for the Higgs in isolation, we look for it produced in association with other heavy particles. Despite these production mechanisms having a far lower rate than isolated Higgs production they have far better signal to background ratios, which makes them look promising. Two modes in particular appear to give encouraging signals; WH production, and tiH production. Both these production modes can be detected in the isolated lepton and two photon channel.

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Plante, Claude. "L'identification des particules chargées ultrarelativistes dans l'émulsion nucléaire." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5631.

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L'étude présentée ici vise à déterminer la relation fonctionnelle existant entre la densité de grains de la trace d'une particule chargée dans l'émulsion nucléaire et le rapport p/mc de cette particule, ou p est la quantité de mouvement, m la masse et c la vitesse de la lumière. L'étude est menée a l'aide des émulsions, de type FUJI ET-7B, exposé dans le cadre de l'expérience E-531 (FNAL), ou se trouvaient réunies des émulsions nucléaires et des détecteurs électroniques, les densités de grains provenant des premières et les quantités de mouvement et les masses des seconds. La relation fonctionnelle observée peut être théoriquement expliquée en termes de deux effets électrodynamiques : la perte d'énergie par ionisation et le rayonnement de transition. Un accord quantitativement satisfaisant ne peut toutefois être obtenu qu'en introduisant dans la modélisation une fonction de résolution pour l'émulsion nucléaire, permettant de tenir compte des caractéristiques du processus photographique. Les modèles de perte d'énergie de Sternheimer (la perte d'énergie restreinte et la perte d'énergie la plus probable), qui ne permettent pas d'inclure une telle fonction, s'avèrent en désaccord, au plan quantitatif, avec les résultats expérimentaux. Un modelé, adapte des travaux de Fano et d'Allison, Bunch et Cobb en particulier, s'accorde avec les résultats expérimentaux si l'on ne tient compte, par le biais de la fonction de résolution, que des transferts d'énergie supérieurs à 90 eV et inférieurs à 1,4 keV. Dans le cas du rayonnement de transition, une fonction de résolution différente est requise, ou ne sont retenus que les transferts d'énergie s'étendant d'environ 450 eV jusqu'à 1,4 keV. La différence dans la fonction de résolution pour les deux effets électrodynamiques peut légitimement être expliquée par le fait qu'il s'agit de deux rayonnements actiniques différents.

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Wang, Gang 1958 Nov 28. "Transverse energy and charged particle multiplicity in 14.6 GeVc proton-nucleus collisions." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28956.

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Transverse energy and charged particle multiplicity produced in 14.6 GeV/c p + Al and p + Pb collisions have been studied using the E814 set-up at the BNL-AGS. Measurements of d$ sigma$/d$E sb{T}$, d$E sb{T}$/d$ eta$,d$ sigma$/d$N sb{c}$, and d$N sb{c}$/d$ eta$ are presented. From the present data the mean transverse energy per particle is obtained and it is compared to values observed in Si induced collisions at the same energy. In contrast to what is observed in nucleus-nucleus collisions, a very weak correlation is found between the transverse energy and the charged particle multiplicity. These results are compared to the predictions of various theoretical models used to describe heavy-ion collisions. The event generators RQMD and HIJET reproduce well the pseudorapidity distribution of both the transverse energy and charged particle multiplicity, whereas FRITIOF fails to reproduce the measured distributions. Contrary to what had been suggested previously in a Si + A study, the present study shows that the pseudorapidity dependence of charged particle multiplicity distributions do not follow KNO scaling.

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Woods, Katharine. "Energy resolution on trigger jets in the ATLAS experiment at the Large Hadron Collider." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104813.

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The most prominent high transverse-momentum products from proton-protoncollisions at the Large Hadron Collider are collimated jets of hadrons. These jets are excellent probes for new physics at the LHC. This thesis presents a thorough investigation of the ATLAS jet energy resolutions of offline reconstructed jets as well as those of the high level trigger. The jet energy resolution is measured using adijet balancing technique on jets reconstructed with different algorithms (anti-kT ,cone) in the pseudorapidity region |η| < 2.5. Results from detailed Monte Carlo studies are compared with results from the collider data, based on up to 35 pb−1 of 7TeV center-of-mass energy proton-proton collisions during the 2010 data taking run. Results show that the jet energy resolution obtained from Monte Carlo simulations agree with resolutions measured in data to within 10%.
La majorité des produits à grande quantité de mouvement transverse résultants des collision proton-proton au LHC sont les gerbes de particules, ou jets. Ces jets sont d'excellentes sources pour sonder la nouvelle physique au LHC. La présente thèse a pour objet l'étude approfondie de la résolution de l'énergie des jets tel que détectés par le détecteur de l'expérience ATLAS, ainsi que pour ceux du système de déclenchement de haut niveau. La résolution de l'énergie des jets est mesurée en appliquant une technique d'équilibrage des jets dans la région de pseudorapidité|η| < 2.5 et qui ont été reconstruits avec des algorithmes différents. Les résultats détaillés d'une étude de simulation Monte Carlo sont comparés aux données du collisionneur prises au cours de l'année 2010, cequi correspond à 35 pb−1 luminosité intégrée provenant de collisions proton-proton à une énergie de centre de masse de 7TeV. Les résultats montrent que la résolution de l'énergie des jets obtenue à partir de simulations Monte Carlo est en accord avec celle mesurée à partir des données à moins de 10%

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Tremblay, Luc 1969. "Effects of a particle spontaneously breaking Lorentz invariance." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38526.

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In this thesis, we add a new vectorial particle to the standard model, a new particle that has the special property of having a vacuum state breaking Lorentz invariance and, therefore, CPT invariance. At the level of energy of the world we live in, this particle is expected to be in this vacuum state and we therefore should see around us some phenomenon that do not respect Lorentz invariance that comes from the interaction of this vectorial particle with ordinary matter. This thesis is presented in two parts. In the first part, we write every possible term involving our new vectorial field with ordinary matter while, in the second part, we calculate the effects of some of those terms and look at any experimental evidence for the calculated effects.

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Buzatu, Adrian. "High-luminosity primary vertex selection in top-quark studies using the Collider Detector at Fermilab." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100780.

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Improving our ability to identify the top quark pair (tt̄) primary vertex (PV) on an event-by-event basis is essential for many analyses in the lepton-plus-jets channel performed by the Collider Detector at Fermilab (CDF) Collaboration. We compare the algorithm currently used by CDF (A1) with another algorithm (A2) using Monte Carlo simulation at high instantaneous luminosities. We confirm that A1 is more efficient than A2 at selecting the tt̄ PV at all PV multiplicities, both with efficiencies larger than 99%. Event selection rejects events with a distance larger than 5 cm along the proton beam between the tt¯ PV and the charged lepton. We find flat distributions for the signal over background significance of this cut for all cut values larger than 1 cm, for all PV multiplicities and for both algorithms. We conclude that any cut value larger than 1 cm is acceptable for both algorithms under the Tevatron's expected instantaneous luminosity improvements.

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Jaroensutasinee, K. "Chaotic motion of charged particles in non-uniform magnetic fields." Thesis, University of Warwick, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282433.

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Keyes, Robert. "New angular search for exotic physics in the photon+jet final state using the ATLAS detector on the LHC." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114367.

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This thesis outlines developments towards a new analysis and search technique for heavy resonances in angular distributions of photon+jet final states for the 2012 data set from the ATLAS detector on the LHC. In particular, a new angular variable tailored to the photon+jet channel was defined which distinguishes between background and expected signals, the corresponding angular observable sensitivity was optimized using ATLAS excited quark samples and JetPhox MC samples, and an optimal mass binning scheme was derived from the measured mass resolution. Ongoing work is being done to publish the analysis.
La présente thèse aborde le développement d'une nouvelle analyse et technique de recherche pour des resonances massives dans les distributions angulaires des états finaux dits photon+jet parmi les données récoltées en 2012 parle détecteur ATLAS du LHC. Une nouvelle variable angulaire développée sur mesure pour le canal photon+jet a d'ailleurs été définie afin de pouvoir distinguer le bruit de fond du signal plus efficacement. La sensitivité de cette observable a été optimisée en utilisant des échantillons Monte Carlo de quarks excités ainsi que du programme JetPhox. Une classification optimale en terme de masse a aussi été dérivée à partir de la mésure de la résolution de masse. Des travaux sont en course afin de publier l'analyse.

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Hoi, Loison. "Cosmological inflation and the primordial power spectrum." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92301.

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Armstrong, Robert E. "Muon neutrino disappearance at MINOS." [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3380059.

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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2009.
Title from PDF t.p. (viewed on Jul 19, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7630. Adviser: Jon Urheim.

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Bang, Jang Young. "Generalized uncertainty principle and Gaussian wave packets in discrete quantum phase space." [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3380062.

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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2009.
Title from PDF t.p. (viewed on Jul 19, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7630. Adviser: Micheal S. Berger.

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Côte, Pierre. "Recherche et analyse d'interactions de neutrinos dans l'émulsion nucléaire." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10204.

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Cette these decrit le travail effectue dans l'emulsion nucleaire pour l'experience E-531 qui avait pour but de mesurer les temps de vie des particules charmees. Les plaques d'emulsion ont ete exposees au faisceau de neutrinos produit par l'interaction de protons de 400 GeV avec une cible de BeO au Fermi National Accelerator Laboratory. Les evenements neutrinos trouves ont ete analyses et les candidats charmes identifies. Un evenement en particulier a ete etudie en profondeur. Il s'agit de la desintegration par interaction faible d'une particule neutre qui n'a pu etre reconstruite en un $D\sp0$. Apres l'essai de plusieurs hypotheses, l'interpretation la plus probable pour l'evenement est celle qui implique la production et la desintegration d'une particule contenant un quark beaute et probablement aussi un quark etrange (le meson $B\sbsp{s}{0}$). Le temps de vie de cette particule d'une etrange beaute serait d'environ 10$\sp{-12}s$. Les distributions de pseudorapidites provenant des evenements neutrino sont analysees a l'aide de moments factoriels. Ces moments manifestent une variation en loi de puissance en fonction de la resolution de la pseudorapidite. Ce comportement est appele intermittence et peut etre caracterise par l'exposant d'echelle $\nu$ qui possede des qualites universelles. La valeur obtenue pour les interactions neutrino-emulsion, $\nu$ = 1.84 $\pm$ 0.14, est plus elevee que pour toute autre interaction. Ceci est le reflet d'un processus dynamique autosimilaire base sur des mecanismes de cascade. L'etude multifractale, effectuee a l'aide des dimensions generalisees et des moments $G\sb{q}$ de Hwa, corrobore cette observation.

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Van, Vlack Cole. "Time dependent complex scaling: Quantum dynamics in strongly perturbed systems." Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/28032.

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We have begun development of a tool for investigating the bound state dynamics of single electron systems in intense fields. This was done by implementing the method of uniform complex scaling in a 1D test system in two different ways and have shown that the use of the "c-norm" in non-Hermitian quantum mechanics can fail for time dependent simulations. We have developed the method of complex backscaling which transforms the wavefunction from the complex scaled space back into real space and have shown that it is more robust than the "c-norm" and predicts the correct ionization when compared to simulations done in real space. We have also begun using the complex scaling method in a 2D NZ model but it seems that the nature of the potential requires a more difficult type of scaling which causes problems within the calculations.

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41

Michaud, Guy. "D-brane bound states and two-dimensional black holes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ44515.pdf.

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Milek, Marko. "Specific ionization in a drift chamber filled with helium-isobutane." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0007/MQ44223.pdf.

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Saab, Tarek. "Study of charmonium final states in B meson decays." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/MQ44266.pdf.

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Breckenridge, Jason C. "Black holes and Dirichlet branes in the theory of strings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ36960.pdf.

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Hung, Ling-Wai. "Inelastic photoproduction of J/[psi] mesons at HERA." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ36985.pdf.

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Kamela, Martin J. "Space-time duality, superduality, and effective actions on anti-de-Sitter space-time." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ64585.pdf.

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Janicek, René. "Search for charmed meson-pion continuum production in semileptonic B decays at CLEO II." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ64583.pdf.

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48

Krop, Dan. "A search for neutral B meson oscillations at the Tevatron collider experiment DO." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3264318.

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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007.
Source: Dissertation Abstracts International, Volume: 68-05, Section: B, page: 3121. Adviser: Rick Van Kooten. "Title from dissertation home page (viewed Jan. 24, 2008)."

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Lin, Fanglei. "Towards full preservation of polarization of proton beam in the AGS." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3297111.

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Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007.
Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1070. Adviser: Shyh-Yuan Lee. Title from dissertation home page (viewed Sept. 29, 2008).

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Miceli, Tia Marie. "Investigations of Standard Model and Exotic Monophoton Signatures at s = 7 TeV." Thesis, University of California, Davis, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3596924.

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This dissertation describes the search for large extra dimensions. Such extra dimensions could solve the hierarchy problem, one of the greatest puzzles in the field of particle physics. The hierarchy problem is the mystery of why gravity is significantly weaker than the electromagnetic, strong, and weak forces. A solution would unify the strength of gravity with the strength of the other forces. There are many possible tests for extra dimensions. Presented is the analysis of proton-proton collisions with final states in which a single photon recoils from an invisible particle. These data were collected with the Compact Muon Solenoid detector during the 2011 Large Hadron Collider run at CERN, in Geneva, Switzerland, and correspond to an integrated luminosity of 5 fb^-1 of proton-proton collisions at a center of mass energy of 7 TeV.

Backgrounds are estimated using data driven techniques for those due to W → νe, hadronic jets, and non-collision backgrounds such as beam remnants faking a photon, and anomalous energy deposits in the electromagnetic calorimeter. The less significant backgrounds are estimated using Monte Carlo simulation, Wγ, dijet, and jet + γ. The irreducible Z(νν)+ γ background was estimated in Monte Carlo for the extra dimension search, but in later studies this component should be estimated by using a ratio of the measured Zγ → μμγ cross section.

The results are consistent with the predicted Standard Model cross section of Z bosons decaying to neutrino pairs. Subsequently, the worlds best limits are placed on the monophoton topology of large extra dimensions. The same analysis provides a measurement of the Z(νν)+γ cross section consistent with next to leading order predictions.

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Dissertations / Theses on the topic 'Elementary Particles and High Energy Physics'

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