Matching Items (22)
Description
An X class solar flare has the potential to remove our satellites from orbit, permanently deactivate our main forms of communication and bring humanity into a technology-free age. By using Geant4, it is possible to simulate several layers of the Earth's atmosphere and send a simulated solar flare and coronal mass ejection. This thesis will show the interaction of photons and protons of various energies with several kilometers of atmosphere.
ContributorsDolghier, Kristian Adrian (Author) / Shovkovy, Igor (Thesis director) / Steinkamp, Brian (Committee member) / Economics Program in CLAS (Contributor) / College of Integrative Sciences and Arts (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
The nucleon resonance spectrum consists of many overlapping excitations. Polarization observables are an important tool for understanding and clarifying these spectra. While there is a large data base of differential cross sections for the process, very few data exist for polarization observables. A program of double polarization experiments has been conducted at Jefferson Lab using a tagged polarized photon beam and a frozen spin polarized target (FROST). The results presented here were taken during the first running period of FROST using the CLAS detector at Jefferson Lab with photon energies ranging from 329 MeV to 2.35 GeV. Data are presented for the E polarization observable for eta meson photoproduction on the proton from threshold (W=1500 MeV) to W=1900 MeV. Comparisons to the partial wave analyses of SAID and Bonn-Gatchina along with the isobar analysis of eta-MAID are made. These results will help distinguish between current theoretical predictions and refine future theories.
ContributorsMorrison, Brian (Author) / Ritchie, Barry (Thesis advisor) / Dugger, Michael (Committee member) / Shovkovy, Igor (Committee member) / Davies, Paul (Committee member) / Alarcon, Ricardo (Committee member) / Arizona State University (Publisher)
Created2011
Description
Monte Carlo methods often used in nuclear physics, such as auxiliary field diffusion Monte Carlo and Green's function Monte Carlo, have typically relied on phenomenological local real-space potentials containing as few derivatives as possible, such as the Argonne-Urbana family of interactions, to make sampling simple and efficient. Basis set methods such as no-core shell model or coupled-cluster techniques typically use softer non-local potentials because of their more rapid convergence with basis set size. These non-local potentials are typically defined in momentum space and are often based on effective field theory. Comparisons of the results of the two types of methods are complicated by the use of different potentials. This thesis discusses progress made in using such non-local potentials in quantum Monte Carlo calculations of light nuclei. In particular, it shows methods for evaluating the real-space, imaginary-time propagators needed to perform quantum Monte Carlo calculations using non-local potentials and universality properties of these propagators, how to formulate a good trial wave function for non-local potentials, and how to perform a "one-step" Green's function Monte Carlo calculation for non-local potentials.
ContributorsLynn, Joel E (Author) / Schmidt, Kevin E (Thesis advisor) / Alarcon, Ricardo (Committee member) / Lebed, Richard (Committee member) / Shovkovy, Igor (Committee member) / Shumway, John (Committee member) / Arizona State University (Publisher)
Created2013
Description
In this thesis, we present the study of several physical properties of relativistic mat- ters under extreme conditions. We start by deriving the rate of the nonleptonic weak processes and the bulk viscosity in several spin-one color superconducting phases of quark matter. We also calculate the bulk viscosity in the nonlinear and anharmonic regime in the normal phase of strange quark matter. We point out several qualitative effects due to the anharmonicity, although quantitatively they appear to be relatively small. In the corresponding study, we take into account the interplay between the non- leptonic and semileptonic weak processes. The results can be important in order to relate accessible observables of compact stars to their internal composition. We also use quantum field theoretical methods to study the transport properties in monolayer graphene in a strong magnetic field. The corresponding quasi-relativistic system re- veals an anomalous quantum Hall effect, whose features are directly connected with the spontaneous flavor symmetry breaking. We study the microscopic origin of Fara- day rotation and magneto-optical transmission in graphene and show that their main features are in agreement with the experimental data.
ContributorsWang, Xinyang, Ph.D (Author) / Shovkovy, Igor (Thesis advisor) / Belitsky, Andrei (Committee member) / Easson, Damien (Committee member) / Peng, Xihong (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2013
Description
For this project, the diffuse supernova neutrino background (DSNB) has been calculated based on the recent direct supernova rate measurements and neutrino spectrum from SN1987A. The estimated diffuse electron antineutrino flux is ∼ 0.10 – 0.59 /cm2/s at 99% confidence level, which is 5 times lower than the Super-Kamiokande 2012 upper limit of 3.0 /cm2/s, above energy threshold of 17.3 MeV. With a Megaton scale water detector, 40 events could be detected above the threshold per year. In addition, the detectability of neutrino bursts from direct black hole forming collapses (failed supernovae) at Megaton detectors is calculated. These neutrino bursts are energetic and with short time duration, ∼ 1s. They could be identified by the time coincidence of N ≥2 or N ≥3 events within 1s time window from nearby (4 – 5 Mpc) failed supernovae. The detection rate of these neutrino bursts could get up to one per decade. This is a realistic way to detect a failed supernova and gives a promising method for studying the physics of direct black hole formation mechanism. Finally, the absorption of ultra high energy (UHE) neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel, is discussed. Results are applied to serval models of UHE neutrino sources. Suppression effects are strong for sources that extend beyond z ∼ 10. This provides a fascinating probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10 – 100. Ultimately this research will examine the detectability of DSNB, neutrino bursts from failed supernovae and absorption effects in the neutrino spectrum.
ContributorsYang, Lili, 1970- (Author) / Lunardini, Cecilia (Thesis advisor) / Alarcon, Ricardo (Committee member) / Shovkovy, Igor (Committee member) / Timmes, Francis (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2013
Description
In this thesis a new method based on the Tight-Binding Linear Muffin Tin Orbital (TB-LMTO) formalism and the Quasiparticle Self-consistent GW (QSGW) approximation is proposed. The method is capable of generating accurate electronic bands structure of large supercells necessary to model alloys structures. The strategy consist in building simple and small hamiltonian from linear Muffin-tin-orbitals (LMTO). Parameters in this hamiltonian are then used to fit the difference in QSGW self-energies and LDA exchange-correlation potentials. The parameter are assumed to transfer to new environments --- a procedure we check carefully by comparing our predicted band to QSGW bands for small supercells. The method possess both the accuracy of the QSGW approximation, (which is the most reliable way to determine energy bands accurately, and yet too expensive for the large supercells required here), and the efficiency of the TB-LMTO method. The accurate and highly efficient hamiltonian is used to predict the electronic and optical transitions of Si1-xGex alloys and SnxSiyGe1-x-y alloys. The goal is to engineer direct band gap material compatible with the silicon technology. The results obtained are compared to available experimental data.
ContributorsDonfack, Hermann Azemtsa (Author) / Van Schilfgaarde, Mark (Thesis advisor) / Dow, John D. (Thesis advisor) / Ponce, Fernando (Committee member) / Ritchie, Barry (Committee member) / Chamberlin, Ralph (Committee member) / Arizona State University (Publisher)
Created2011
Description
The current observable universe is made of matter due to baryon/antibaryon asymmetry. The Deep Underground Neutrino Experiment is an international experiment through the Fermi National Accelerator Laboratory that will study neutrinos. In this study, the detection efficiency for low energy supernova neutrinos was examined in order to improve energy reconstruction for neutrino energies less than 40 MeV. To do this, supernova neutrino events were simulated using the LarSoft simulation package with and without background. The ratios between the true data and reconstructed data were compared to identify the deficiencies of the detector, which were found to be low energies and high drift times. The ratio between the true and reconstructed data was improved by applying the physical limits of the detector. The efficiency of the improved ratio of the clean data was found to be 93.2% and the efficiency of the improved ratio with the data with background was 82.6%. The study suggests that a second photon detector at the far wall of the detector would help improve the resolutions at high drift times and low neutrino energies.
ContributorsProcter-Murphy, Rachel Grace (Co-author) / Procter-Murphy, Rachel (Co-author) / Ritchie, Barry (Thesis director) / LoSecco, John (Committee member) / School of Earth and Space Exploration (Contributor) / Department of Physics (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
In this project, we created a code that was able to simulate the dynamics of a three site Hubbard model ring connected to an infinite dissipative bath and driven by an electric field. We utilized the master equation approach, which will one day be able to be implemented efficiently on a quantum computer. For now we used classical computing to model one of the simplest nontrivial driven dissipative systems. This will serve as a verification of the master equation method and a baseline to test against when we are able to implement it on a quantum computer. For this report, we will mainly focus on classifying the DC component of the current around our ring. We notice several expected characteristics of this DC current including an inverse square tail at large values of the electric field and a linear response region at small values of the electric field.
ContributorsJohnson, Michael (Author) / Chamberlin, Ralph (Thesis director) / Ritchie, Barry (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
A search is underway to find baryon resonances that have been predicted, but yet remain unobserved. Nucleon resonances, due to their broad energy widths, overlap and must be disentangled in order to be identified. Meson photoproduction observables related to the orientation of the spin of the incoming photon and the spin of the target proton are useful tools to deconvolve the nucleon resonance spectrum. These observables are particularly sensitive to interference between phases of the complex amplitudes. A set of these observables has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab with linearly-polarized photons having energies from 725 to 1575 MeV with polar angle values of cos(theta) between -0.8 and 0.9 and transversely-polarized protons in the Jefferson Lab FRozen Spin Target (FROST). By fitting neutron yields from gamma p -> pi^+ n over azimuthal scattering angle, the observables \H and P have been extracted. These observables manifest as azimuthal modulations in the yields for the double-polarization experiment. Preliminary results for these observables will be presented and compared with predictions provided by the SAID Partial-Wave Analysis Facility.
ContributorsLee, Robert John (Author) / Dugger, Michael (Thesis director) / Ritchie, Barry (Committee member) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
In nuclear physics, there is a discrepancy between theory and experiment concerning the number of existing nucleon resonances. Current models predict far more states than have been observed. In particular, few searches have found excited nucleon resonances with energies above 2.2 GeV in the K Lambda channel. To investigate high-mass nucleon resonances, efficiency-corrected yields of the reaction ep --> e K+ Lambda(1520) --> e K+ K- p in the center-of-mass energy range 2.1-4.5 GeV are constructed utilizing Jefferson Lab's CLAS12 detector. This paper presents the results of an analysis searching for high-mass nucleon resonances in the K Lambda channel between 2.1-4.5 GeV.
ContributorsOsar, Rebecca (Author) / Dugger, Michael (Thesis director) / Ritchie, Barry (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor) / School of International Letters and Cultures (Contributor)
Created2023-05