Browsing by Author "Harton, John, committee member"
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Item Open Access A measurement of muon neutrino charged-current interactions with a charged pion in the final state using the NOνA near detector(Colorado State University. Libraries, 2023) Rojas, Paul Nelson, author; Buchanan, Norm, advisor; Lee, Siu Au, committee member; Harton, John, committee member; Kokoszka, Piotr, committee memberThe NOνA experiment is a long-baseline neutrino experiment hosted by Fermilab. The intense NuMI neutrino beam, combined with NOνA Near Detector, provides the opportunity to study neutrino interactions at an unprecedented level. The goal of this analysis is to measure the rate of muon-neutrino charged-current interactions in the NOνA near detector resulting in the production of one muon and at least one charged pion. This thesis will present the result of the double differential cross section measurement of this process in muon kinematics of energy and angle. Excesses in the extracted signal (greater than 25%), relative to the simulation, were found at large scattering angles. These excesses were greater than the estimated uncertainties (∼15%).Item Open Access A measurement of the double-differential electron antineutrino charged-current inclusive cross section in the NOvA near detector(Colorado State University. Libraries, 2023) Doyle, Derek, author; Buchanan, Norm, advisor; Gelfand, Martin, committee member; Harton, John, committee member; Norman, Andrew, committee member; Pouchet, Louis-Noël, committee memberThe neutrino is a fundamental particle of the universe that was first hypothesized in 1930 by Wolfgang Pauli to explain the observed energy distribution of outgoing electrons produced from beta-decay. Since then, it has been discovered that there are at least three types, or flavors, of neutrinos and that they oscillate between these flavors as they travel through space and time. This discovery proved that neutrinos have a non-zero mass and positioned neutrino oscillations to provide a window into understanding the matter/antimatter asymmetry in the universe. Principle to all neutrino measurements is an accurate and robust interaction model over a large range of energies, and measurements to support the model. Of particular importance to the NuMI Off-axis νe Appearance (NOvA) neutrino oscillation experiment is the energy range from 1 to 10 GeV, where Quasi-Elastic (QE), Meson-Exchange Current (MEC), and Deep Inelastic Scattering (DIS) interactions all contribute significantly. Using neutrinos from the Neutrinos at the Main Injector (NuMI) beam and the NOvA near detector, the first double-differential electron antineutrino charged-current inclusive cross section is measured and compared to various interaction models implemented within the genie Generator framework, version 3. Good agreement is observed between measurement and a genie model tuned to NOvA data.Item Open Access Accelerating NOvA's Feldman-Cousins procedure using high performance computing platforms(Colorado State University. Libraries, 2019) Doyle, Derek, author; Buchanan, Norm, advisor; Harton, John, committee member; Pouchet, Loius-Noël, committee memberIn order to assess the compatibility between models containing physically constrained parameters and small-signal data, uncertainties often must be calculated by Monte Carlo simulation to account for non-normally distributed errors. This is the case for neutrino oscillation experiments, where neutrino-matter weak interactions are rare and beam intensity at the far site is low. The NuMI Off-axis νe Appearance (NOvA) collaboration attempts to measure the parameters governing neutrino oscillations within the PMNS oscillation model by comparing model predictions to a small data set of neutrino interactions. To account for non-normality, NOvA uses the computationally intensive Feldman-Cousins (FC) procedure, which involves fitting thousands of independent pseudoexperiments to generate empirical distribution functions that are used to calculate the significance of observations. I, along with collaborators on NOvA and Scientific Discovery through Advanced Computing: High Energy Physics Data Analytics (SciDAC-4) collaborations, have implemented the FC procedure utilizing the High Performance Computing (HPC) facilities at the National Energy Research Scientific Computing Center (NERSC). With this implementation, we have successfully processed NOvA's complete FC corrections for our recent neutrino + antineutrino appearance analysis in 36 hours: a speedup factor of 50 as compared to the methods used in previous analyses.Item Open Access Cosmogenic background rejection for the sterile neutrino search with the Short-Baseline Neutrino Program far detector(Colorado State University. Libraries, 2020) Hilgenberg, Christopher M., author; Wilson, Robert J., advisor; Harton, John, committee member; Toki, Walter, committee member; Zhu, Wen, committee memberAs the Short-Baseline Neutrino Program Far Detector, the ICARUS liquid argon time-projection chamber will operate at shallow depth and therefore be exposed to the full surface flux of cosmic rays. This poses a problematic background to the sterile neutrino search. A direct way to reject this background is to surround the cryostat with a detector capable of tagging incident cosmic muons with high efficiency, the Cosmic Ray Tagging System (CRT). I have worked to develop the CRT detector hardware and the simulation and reconstruction software. This system, currently undergoing installation, is approximately 25% commissioned and taking data. I have developed a powerful method for cosmogenic background rejection utilizing the CRT and Photon Detection System. Results from a simulation based study, informed by CRT data, demonstrate the power of the technique in rejecting cosmogenic events with little adverse impact on the neutrino sample.Item Open Access External dose assessment in the Ukraine following the Chernobyl accident(Colorado State University. Libraries, 2014) Frazier, Remi Jordan Lesartre, author; Borak, Thomas, advisor; Brandl, Alex, committee member; Harton, John, committee memberWhile the physiological effects of radiation exposure have been well characterized in general, it remains unclear what the relationship is between large-scale radiological events and psychosocial behavior outcomes in individuals or populations. To investigate this, the National Science Foundation funded a research project in 2008 at the University of Colorado in collaboration with Colorado State University to expand the knowledge of complex interactions between radiation exposure, perception of risk, and psychosocial behavior outcomes by modeling outcomes for a representative sample of the population of the Ukraine which had been exposed to radiocontaminant materials released by the reactor accident at Chernobyl on 26 April 1986. In service of this project, a methodology (based substantially on previously published models specific to the Chernobyl disaster and the Ukrainian population) was developed for daily cumulative effective external dose and dose rate assessment for individuals in the Ukraine for as a result of the Chernobyl disaster. A software platform was designed and produced to estimate effective external dose and dose rate for individuals based on their age, occupation, and location of residence on each day between 26 April 1986 and 31 December 2009. A methodology was developed to transform published 137Cs soil deposition contour maps from the Comprehensive Atlas of Caesium Deposition on Europe after the Chernobyl Accident into a geospatial database to access these data as a radiological source term. Cumulative effective external dose and dose rate were computed for each individual in a 703-member cohort of Ukrainians randomly selected to be representative of the population of the country as a whole. Error was estimated for the resulting individual dose and dose rate values with Monte Carlo simulations. Distributions of input parameters for the dose assessment methodology were compared to computed dose and dose rate estimates to determine which parameters were driving the computed results. The mean external effective dose for all individuals in the cohort due to exposure to radiocontamination from the Chernobyl accident between 26 April 1986 and 31 December 2009 was found to be 1.2 mSv; the geometric mean was 0.84 mSv with a geometric standard deviation of 2.1. The mean value is well below the mean external effective dose expected due to typical background radiation (which in the United States over this time period would be 12.0 mSv). Sensitivity analysis suggests that the greatest driver of the distribution of individual dose estimates is lack of specific information about the daily behavior of each individual, specifically the portion of time each individual spent indoors (and shielded from radionuclides deposited on the soil) versus outdoors (and unshielded).Item Open Access Measurement of the inclusive electron neutrino charged-current cross section in the NOvA near detector(Colorado State University. Libraries, 2019) Judah, Matthew A., author; Buchanan, Norm, advisor; Gelfand, Martin, committee member; Harton, John, committee member; Pallickara, Sangmi, committee memberThis thesis describes the methods used to extract the inclusive νₑ charged-current cross section in the NOνA near detector using data collected from November 2014 to February 2017, corresponding to an exposure of $8.09 x 10²⁰ protons-on-target of a primarily neutrino beam. The near detector is located at Fermilab, 800 m from the primary target. The neutrino beam peaks near 2 GeV and is able to probe a variety of different neutrino-nucleus interactions through their final-state characteristics. The flux-integrated double-differential cross section is measured with respect to the final-state electron kinematics, as well as the total cross-section as a function of neutrino energy integrated over the same phase space used for the double-differential measurement.Item Open Access Measurement of νμ-induced charged-current single π⁺ production on H₂O(Colorado State University. Libraries, 2015) Assylbekov, Shamil M., author; Wilson, Robert J., advisor; Toki, Walter, committee member; Harton, John, committee member; Berger, Bruce, committee member; Hulpke, Alexander, committee memberT2K is an international collaboration that has constructed an experiment in Japan to investigate the properties of the neutrino. It consists of two near detectors, ND280 and INGRID, and a far detector - Super-Kamiokande. ND280 has multiple sub-detectors with the π⁰ detector (PØD) being of most importance to this analysis. This work describes the first measurement of neutrino cross section for charged-current single positively charged pion (CC1π⁺) interaction channel on water (H₂O) using the PØD as target and detector. The PØD detector has been taking neutrino interaction data since 2009 in configurations with and without an integrated water target. Using a statistical water-in/water-out event rate subtraction, a measurement of the νμ-induced CC1π⁺ cross section on water is reported to be ‹σ› = 1.10 x 10⁻³⁹ +0.39·10⁻³⁹/-0.36·10⁻³⁹ cm², where the result is provided in the form of a single-bin cross section integrated over the entire T2K neutrino energy range. The measurement is based on a sample of 2,703 events selected from beam runs of $2.64 x 10²⁰ protons-on-target (POT) with the PØD water-in configuration, and 2,187 events selected from $3.71 x 10²⁰ POT with the water-out configuration. The corresponding Monte Carlo simulation predicted numbers of background events to be 1,387.2 and 1,046.0 for the water-in and water-out detector configurations, respectively. The accuracy of the result is dominated by flux and cross section models uncertainties. The data favors a systematically smaller cross section when compared to the model but within the uncertainties it is consistent with the Monte Carlo simulation prediction of $1.26 x 10⁻³⁹cm². The result, its significance, and the strategy for future CC1π⁺ measurements are discussed in conclusion.Item Open Access Measurements of electron-ion collision rates and Rydberg atom populations in ultracold plasmas by using short electric field pulses(Colorado State University. Libraries, 2017) Chen, Wei-Ting, author; Roberts, Jacob, advisor; Robinson, R. Steve, committee member; Harton, John, committee member; Krapf, Diego, committee memberUltracold plasmas are good tools for studying fundamental plasma physics. In particular, these plasmas are well-suited to study so-called strong coupling physics the physics of plasmas where nearest-neighbor Coulomb interactions become large enough to cause spatial correlations and break assumptions. An ultracold plasma makes such a good tool because it is it is free of interactions with neutral atoms, and has a well controlled and tunable initial conditions. The UCPs in this work were created from the photoionization of cold 85Rb atoms. The experiments described in this thesis are focused on the measurements of damping of electron center-of-mass oscillations. We developed a method that uses two short electric field pulses to map the temporal profile of the oscillation amplitude. We found that the damping of such oscillations can result from dephasing which is a collisionless mechanism or from electron-ion collisions or a combination of both. Thus, we separate the study of two pulse measurements into two parts. The first part of the two short electric field pulse measurement is about the measurements and modeling of in the collisionless damping regime. The second part will focus on the regime where the damping is dominated by electron-ion collisions where we not only observed strong coupling influence on electron-ion collision rates, but also saw break down of one or more standard assumptions used in plasma physics calculations. Rydberg atoms can be formed in ultracold plasmas through three-body recombination process. Our setup was capable of measuring Rydberg atoms in a energy range above the bottleneck energy. We measured the Rydberg populations at different temperatures, and our preliminary results agree well with a parameter-free calculation. However, there are some unexplained parts of our measurements on early time Rydberg populations. This means more studies are needed in the future in order to interpret our results and make use of them. Future work includes measurements of the strong coupling influence on electron-ion collision rates in a magnetized ultracold plasma, measurement of Rydberg population below the bottleneck energy, a detailed study of evaporations in ultracold plasmas.Item Open Access Metal oxides as buffer layers in polycrystalline CdTe thin-film solar cells(Colorado State University. Libraries, 2021) Pandey, Ramesh, author; Sites, James, advisor; Sampath, W.S., committee member; Ross, Kate, committee member; Harton, John, committee memberThe optical band-gap of 1.5 eV and absorption coefficient the order of 105 cm-1 makes CdTea very attractive absorber for thin-film solar cells. This dissertation explores methods to improve both the front, or emitter, part of the cell and the back contact to the CdTe-based thin-film solar cells. The choice of an n-type emitter partner for CdTe based solar cells is crucial to the overall power conversion efficiency. In comparison to the traditional CdS emitter, metal oxides such as ZnO, MgO, and the ternary alloy MgxZn1-xO have large optical band-gaps making them transparent to most of the solar spectrum and an ideal emitter layer adjacent to light-facing side of the absorber in a superstrate configuration. The optical and electrical properties of MgxZn1-xO emitters can be modulated by varying the elemental ratio of x = Mg:(Mg + Zn) in the ternary alloy. Tracing the variation of the conversion efficiency as a function of Mg fraction in MgxZn1-xO emitter, an optimal Mg fraction of x = 0.15 was found to produce highest efficiency for the CdTe-based thin-film solar cells. Photoelectron spectroscopy demonstrated the conduction band offset at the emitter/absorber interface transitions from a cliff like -0.1 eV for x = 0.00 to a spike like 0.2 eV at the optimal x = 0.15. Photoluminescence and low-temperature current-voltage measurements showed that the interface between MgZnO and the CdSeTe is well passivated for x = 0.15. Further increase in the Mg fraction however increases the band offset between the emitter/absorber leading to distortions of J-V curves under various illumination conditions. Light soaking experiments and numerical simulations show that an insufficient density of carriers in the MgZnO due to the compensating defects causes these distortions: a failure of superposition of light and dark curves referred to as cross over, and distortion from normal current voltage behavior under spectra filtered illumination. An extrinsic doping of the emitter is critical to rectify these distortions and Ga-doped MgZnO was employed to experimentally demonstrate a cure to these J-V distortions characteristic of an undoped MgZnO emitter. It paves pathway to increase the n-type carrier density in the MgZnO emitter. The group-V doping of CdTe has shown potential to improve open circuit voltage, with level of doping in absorber the order of 1016 cm-3 and lifetimes of hundreds of ns. Numerical device simulations demonstrate that doping the emitter layer is essential and a particular challenge if the doping in the absorber is high. The results find the carrier concentration in emitter should be higher than the doping in the absorber to attain high open-circuit voltage in the highly doped CdTe-absorbers possible with arsenic doping. Various back contact metals like Ag, Co, Pt and metalloids like Te, and Se with different work functions were used to make an ohmic contact with the CdTe back surface. The use of a buffer layer behind the bare CdTe surface is found to be critical to the device performance. A thin 30-nm layer of Te have become the preferred choice of back buffer layer. Metal oxides like TeOx has been introduced as back buffer between the CdTe absorber and Te back contact to study their effect in device performance. The study finds that a double CdCl2 passivation procedure before and after the deposition of oxides is critical to the performance of these solar cells. Devices with the TeOx and the Te layer as back buffer demonstrated a power conversion efficiency in excess of 17 % without the incorporation of dopant in the absorber. Such a result is significant, as extrinsic dopants in CdTe-based absorbers often introduce defects in the absorber leading to increased recombination and degradation of cell performance particularly if the absorber is doped with Cu. Spectral and time resolved photoluminescence measurements carried out with illumination from front glass side show such cells have improved minority carrier lifetimes. The rear TRPL illumination to probe a CdTe/TeOx surface measured lifetimes of few ns indicative of the TeOx as a back buffer layer to mitigate the effects of large defects on a free CdTe surface. These results demonstrate metal oxides as a promising candidates for back buffer layers, and passivating back contact for hole selectivity in the CdTe-based solar cells.Item Open Access Modular group and modular forms(Colorado State University. Libraries, 2010) Schmidt, Eric, author; Hulpke, Alexander, advisor; Achter, Jeff, committee member; Cavalieri, Renzo, committee member; Harton, John, committee memberWe prove some results about the structure of SL2(Z) and related groups. We define modular forms for this group and develop the basic theory. We then use the theory of lattices to construct examples of modular forms.Item Open Access Muon neutrino reconstruction with machine-learning techniques at the ICARUS detector(Colorado State University. Libraries, 2024) Mueller, Justin J., author; Mooney, Michael, advisor; Harton, John, committee member; Brandl, Alexander, committee member; Brewer, Samuel, committee member; Terao, Kazuhiro, committee memberThe ICARUS T600 LArTPC detector successfully ran for three years at the underground LNGS laboratories, providing a first sensitive search for LSND-like anomalous electron neutrino appearance in the CNGS beam. After a significant overhauling at CERN, the T600 detector has been placed in its experimental hall at Fermilab, fully commissioned, and the first events observed with full detector readout. Regular data-taking began in May 2021 with neutrinos from the Booster Neutrino Beam (BNB) and neutrinos six degrees off-axis from the Neutrinos at the Main Injector (NuMI). Modern developments in machine learning have allowed for the development of an end-to-end machine-learning-based event reconstruction for ICARUS data. This reconstruction folds in 3D voxel-level feature extraction using sparse convolutional neural networks and particle clustering using graph neural networks to produce outputs suitable for physics analyses. The analysis presented in this thesis demonstrates a high-purity and high-efficiency selection of muon neutrino interactions in the BNB suitable for the physics goals of the ICARUS experiment and the Short-Baseline Neutrino Program.Item Open Access Neutrino oscillation parameter sensitivity in future long-baseline experiments(Colorado State University. Libraries, 2014) Bass, Matthew, author; Wilson, Robert J., advisor; Harton, John, committee member; Toki, Walter, committee member; Zhou, Wen, committee memberThe study of neutrino interactions and propagation has produced evidence for physics beyond the standard model and promises to continue to shed light on rare phenomena. Since the discovery of neutrino oscillations in the late 1990s there have been rapid advances in establishing the three flavor paradigm of neutrino oscillations. The 2012 discovery of a large value for the last unmeasured missing angle has opened the way for future experiments to search for charge-parity symmetry violation in the lepton sector. This thesis presents an analysis of the future sensitivity to neutrino oscillations in the three flavor paradigm for the T2K, NOνA, LBNE, and T2HK experiments. The theory of the three flavor paradigm is explained and the methods to use these theoretical predictions to design long baseline neutrino experiments are described. The sensitivity to the oscillation parameters for each experiment is presented with a particular focus on the search for CP violation and the measurement of the neutrino mass hierarchy. The variations of these sensitivities with statistical considerations and experimental design optimizations taken into account are explored. The effects of systematic uncertainties in the neutrino flux, interaction, and detection predictions are also considered by incorporating more advanced simulations inputs from the LBNE experiment.Item Open Access Spin wave characterization in a 1D YIG magnonic crystal(Colorado State University. Libraries, 2023) Compton, Lia, author; Buchanan, Kristen, advisor; Harton, John, committee member; Prieto, Amy, committee memberIn this thesis, I will analyze and discuss features of spin wave propagation characteristics measured in a one-dimensional (1D) yttrium iron garnet (YIG) magnonic crystal using time-resolved Brillouin light scattering (TR-BLS) measurements. Magnonic crystals are a promising candidate to aid in developing spin-based devices that exploit the spin of the electron since magnonic crystals can be used to control the information transmitted by spin waves. In magnonic crystals, periodic modulation of the material properties is used to create a band structure and hence allow or suppress the propagation of spin waves with specific frequencies. To better understand spin wave propagation in a 1D YIG magnonic crystal, (TR-BLS) measurements were used to map out the temporal and spatial evolution of spin wave pulses at different frequencies. By analyzing the TR-BLS data with a cross-correlation method, the group velocities were determined at different frequencies and a better understanding of the changes in the pulse shape is gained. The TR-BLS data show that multiple width-quantized spin wave modes are present and highlights the importance of considering the two-dimensional nature of spin wave propagation, even in a one-dimensional system.Item Open Access Verification of background reduction in a liquid scintillation counter(Colorado State University. Libraries, 2013) Magenis, Marilyn Alice, author; Brandl, Alexander, advisor; Johnson, Thomas E., committee member; Volckens, John, committee member; Harton, John, committee memberA new method for subtraction of extraneous cosmic ray background counts from liquid scintillation detection has been developed by Hidex™. The method uses a background counter located beneath the liquid scintillation detector, the guard, to account for background signals. A double to triple coincidence counting methodology is used to reduce photomultiplier noise and to quantify quench. It is important to characterize the interactions from background in any new system. Characterizing interactions in the instrument will help to verify the accuracy and efficiency of the guard by determining the noise cancellation capabilities of the liquid scintillation counter. The liquid scintillation counter and guard detector responses were modeled using MCNP for the expected cosmic ray interactions at the instrument location and altitude in Fort Collins, CO. Cosmic ray interactions in the detector are most relevant to examine because of their predominance due to the higher elevation in Fort Collins. The cosmic ray interactions that are most important come from electron, positron, and gamma interactions. The expected cosmic ray interactions from these particles were modeled by using a cosmic ray library that determines the cosmic rays that are most likely to occur at an altitude of 2100 meters. The model predictions were then compared to the instrument background measurements. The results suggest that the cosmic ray contribution to the instrument background is negligible.Item Open Access What controls the variability of oxygen in the subpolar North Pacific(Colorado State University. Libraries, 2011) Takano, Yohei, author; Ito, Takamitsu, advisor; Thompson, David, committee member; Deutsch, Curtis, committee member; Harton, John, committee memberDissolved oxygen is a widely observed chemical quantity in the oceans along with temperature and salinity. Changes in the dissolved oxygen have been observed over the world oceans. Observed oxygen in the Ocean Station Papa (OSP, 50°N, 145°W) in the Gulf of Alaska exhibits strong variability over interannual and decadal timescales, however, the mechanisms driving the observed variability are not yet fully understood. Furthermore, irregular sampling frequency and relatively short record length make it difficult to detect a low-frequency variability. Motivated by these observations, we investigate the mechanisms driving the low-frequency variability of oxygen in the subpolar North Pacific. The specific purposes of this study are 1) to evaluate the robustness of the observed low-frequency variability of dissolved oxygen and 2) to determine the mechanisms driving the observed variability using statistical data analysis and numerical simulations. To evaluate the robustness of the low-frequency variability, we conducted spectral analyses on the observed oxygen at OSP. To address the irregular sampling frequency we randomly sub-sampled the raw data to form 500 ensemble members with a regular time interval, and then performed spectral analyses. The resulting power spectrum of oxygen exhibits a robust low-frequency variability and a statistically significant spectral peak is identified at a timescale of 15-20 years. The wintertime oceanic barotropic streamfunction is significantly correlated with the observed oxygen anomaly at OSP with a north-south dipole structure over the North Pacific. We hypothesize that the observed low-frequency variability is primarily driven by the variability of large-scale ocean circulation in the North Pacific. To test this hypothesis, we simulate the three-dimensional distribution of oxygen anomaly between 1952 to 2001 using data-constrained circulation fields. The simulated oxygen anomaly shows an outstanding variability in the Gulf of Alaska, showing that this region is a hotspot of oxygen fluctuation. Anomalous advection acting on the climatological mean oxygen gradient is the source of oxygen variability in this simulation. Empirical Orthogonal Function (EOF) analyses of the simulated oxygen show that the two dominant modes of the oxygen anomaly explains more than 50% of oxygen variance over the North Pacific, that are closely related to the dominant modes of climate variability in the North Pacific (Pacific Decadal Oscillation and North Pacific Oscillation). Our results imply the important link between large-scale climate fluctuations, ocean circulation and biogeochemical tracers in the North Pacific.