Browsing by Subject "Particles (Nuclear physics)"
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Item A study of the possible binding of a cascade hyperon in a nucleus(Texas Tech University, 1962-05) Hardcastle, Donald LeeNot availableItem Background field effects on particle physics(2005) Tinsley, Todd Michael; Dicus, Duane A.Item Cosmology driven by physics beyond the standard model(2007-12) Žanić, Marija, 1972-; Paban, SoniaThis dissertation investigates several problems inspired by the interplay of cosmology and theories beyond the Standard Model of particle physics. The first part of this work is a study of time evolution of unstable dS[subscript p] x S[superscript q] configurations with flux in theories of gravity with a cosmological constant. We find that, depending on the flux, these configurations either evolve towards newly identified stable solutions with a smaller final effective cosmological constant, or tend toward decompactication of the internal sphere. In the second part, we investigate the problem of evolution of vacuum bubbles in inhomogeneous backgrounds. It is expected that the process of inflation will signifcantly smooth out spatial inhomogeneities. However, the initial conditions for inflation are often taken in the already homogeneous and isotropic FRW form, even though it is assumed that initial homogeneity is not necessary for the onset of inflation. We determine the effects of certain inhomogeneities, introduced in the curvature of the outside spacetime, on the propagation of bubbles, and how these effects differ depending on whether the perspective taken is that of the outside observer or an observer on the bubble. The last part of the dissertation presents a model for a novel component of the energy density of the universe. The observational limits on the present energy density allow for a component that redshifts like 1/a² and can contribute significantly to the total. We show that one possible origin for such a contribution is that the universe has a toroidal topology with "wound" scalar fields around its cycles.Item Darwinian evolution: the mutation of a weakly relativistic lagrangian(2004) Krause, Todd Brandon; Morrison, Philip J.The work studies Darwin’s order-(v/c)2 approximation to the relativistic interaction of classical charged particles. The first part presents an in- troduction to the methods of symplectic reduction in the Newtonian two- body problem and then applies these to a two-body Darwin interaction. The momentum-dependent interaction of the Darwin system plays an important role in the ability to reduce to a system of one degree of freedom. Circular orbits are sought, and it is shown that two of the three possible orbits are prohibited by velocity conditions. The second part of the work derives a self-consistent Darwin particle theory from a Lagrangian for electromagnetic fields coupled to particles. The resulting particle Lagrangian agrees with previous results. A similar procedure is followed to obtain a Low-Darwin system, coupling the self-consistent Darwin theory to the Vlasov equation.Item Hadron-quark hybrid model and the structure of light nuclei(Texas Tech University, 1991-05) Abokor, Abdirahman Yusuf.Item Investigation into compactifed dimensions: Casimir energies and phenomenological aspects.(2009-01-07T22:13:03Z) Obousy, Richard K.; Cleaver, Gerald B.; Physics.; Baylor University. Dept. of Physics.A central theme in this dissertation is the notion of the quantum vacuum. To a particle physicist, the term 'vacuum' means the ground state of a theory. In general, this ground state must obey Lorentz invariance, at least with regards to 3 spatial dimensions, meaning that the vacuum must look identical to all observers. At all energies probed by experiments to date, the universe is accurately described as a set of quantum fields. If we take the Fourier transform of a free quantum field, each mode of a fixed wavelength behaves like a simple harmonic oscillator. A quantum mechanical property of a simple harmonic oscillator is that the ground state exhibits zero-point fluctuations as a consequence of the Heisenberg Uncertainty Principle. These fluctuations give rise to a number of phenomena; however, two are particularly striking. First, the Casimir Effect, which will be examined in detail in this dissertation is arguably the most salient manifestation of the quantum vacuum. In its most basic form it is realized through the interaction of a pair of neutral parallel conducting plates. The presence of the plates modifies the quantum vacuum, and this modification causes the plates to be pulled toward each other. Second is the prediction of a vacuum energy density, which is an intrinsic feature of space itself. Many attempts have been made to relate this vacuum energy to the cosmological constant Lambda, which is a common feature in modern cosmology; however, calculations are typically plagued either by divergences or by ridiculously high predictions which are far removed from observation. This chapter will first provide a brief historical review of the vacuum and then discuss in detail some of the attempts to explain the vacuum in the language of Quantum Field Theory (QFT).Item Mass levels of some elementary particles(Texas Tech University, 1985-05) Yimbo, Christopher SikukuThe structure and mass levels of some elementary particles are presented. A non-relativistic bound state model has been used to describe the J \ψ and ψ' particles. The order of levels, 1S - 2P - 2S, as observed in the ψ, X, ψ’ spectroscopy is generally assumed. We introduce as interaction potential a confining potential (Vc) in combination with a Coulomb-like potential -g^2/r to try to prove that the 2S level is above the 2P level. Our result shows that the order of levels is what we believe it to be: IS - 2P - 2S.Item Probing exotic physics with pulsating white dwarfs(2007) Kim, Agnès; Winget, D. E.Item Probing exotic physics with pulsating white dwarfs(2007-05) Kim, Agnès, 1975-; Winget, Donald Earl, 1955-Item Self-consistent dynamics of nonlinear phase space structures(2004) Eremin, Denis; Berk, H. L.This thesis investigates the self-consistent dynamics of nonlinear ”hole” and ”clump” phase space structures and the nonlinear modes supported by the structures in the presence of dissipation due to the background plasma. A system consisting of a single mode driven by a weakly destabilizing distribution function in a dissipative medium close to the threshold of linear instability exhibits explosive instability. This instability results in the formation of the phase space structures and the corresponding modes. The holes and clumps were expected to persist for an appropriate collisional time scale. However, for certain initial conditions Fokker-Planck calculations for the nonlinear system abruptly break down in the course of the calculation. We find that this is because an adiabatic description of phase space structures at zero collisionality does not necessarily lead to continual adiabatic frequency sweeping. For a class of initial distribution functions criteria are found that detervii mine whether adiabatic frequency sweeping will continue indefinitely or suddenly terminate. For certain other initial distribution functions that describe the predominantly deeply trapped particles, critical points may be encountered where the adiabatic analysis fails to yield a unique solution. Except for establishing boundary conditions, the contribution of passing particles is found to be unimportant in the dynamics of the phase space structures within the framework of the adiabatic description. We derived a self-consistent dispersion relation for the perturbed eigenmodes of the system and benchmarked the result with the dispersion relation obtained earlier in Ref. [53] and demonstrated their agreement. We analyzed this dispersion relation and demonstrated that the critical points of the adiabatic theory occur exactly where linear instability is triggered. Numerical runs were performed to test both the adiabatic theory and the instability analysis of a BGK (Bernstein-Greene-Kruskal) mode for a model problem where the distribution function of passing particles has zero slope with respect to the action variable. This problem has same essential features as the problem where the slope of the passing particle distribution function is constant. In particular, linear instability of the same nature is also predicted to arise whenever adiabatic analysis predicts termination of frequency sweeping. This procedure has the virtue of enabling a precise comparison of the theory with the simulations and indeed it does so until instability sets in. The model problem was also used to demonstrate the agreement between the numerical growth rate and the growth rate predicted in the instability analysis. Then a passing particle distribution function was used that has a constant slope with respect to the action variable, and it too showed agreement with the theory for the evolution of the adiabatic phase, for where the onset of the instability was predicted to occur, and for where the persistence of the phase space structures after the instability relaxation. Both cases showed that after the instability dies away, smaller phase space structures still persist and the frequency sweeping continues at a slower rate. The numerical simulations demonstrated the additional effect that several generations of the nonlinear phase space structures are often produced. The numerical data shows that the mode amplitude is reduced when there are neighboring modes. We considered two possible mechanisms that may account for such reduction of the primary mode amplitude. In one mechanism, the particle orbits remain regular and the mode amplitude reduction is caused by the accumulation (in the case of a clump) [or depletion in the case of a hole] of the passing particle distribution of one of the modes, because it is part of the trapped particle region of the other mode. The other mechanism is the chaotic erosion of trapped particles near the separatrix.Item A study of angular asymmetries in the rare decay B (right arrow) K*[lambda]⁺[lambda]⁻(2008-08) Schilling, Chris James, 1980-; Ritchie, Jack L., 1955-This dissertation describes studies of the rare quark transition process b → s`+` −, in particular the B meson decay B → K∗ ` +` − where the ` +` − is either e +e − or µ +µ −. These decays are highly suppressed in the Standard Model and could be strongly affected by new physics. The angular observables describing the lepton forward-backward asymmetry and the longitudinal K∗ polarization are measured in this mode. The measurements were performed using the BABAR detector at the SLAC PEPII storage ring running at the Υ(4S) resonance. The analysis was performed on a 349 fb−1 sample corresponding to 384 million BB pairs. The data was collected over a period of six years beginning in 1999. For low dilepton invariant masses, m`` < 2.5 GeV/c2 , we measure a lepton forward backward asymmetry AFB = 0.24+0.18 −0.23 ± 0.05 and a K∗ longitudinal polarization FL = 0.35 ± 0.16 ± 0.04. For m`` > 3.2 GeV/c2 , we measure AFB = 0.76+0.52 −0.32 ± 0.07 and FL = 0.71+0.20 −0.22 ± 0.04.