Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages [181]-205) and index. / The IceCube detector opens a new window into our universe; valuable for both astronomy and particle physics. This thesis spans a wide range of topics that are bound together by a common theme: the development and application of new statistical and computational methods for analysing data from particle and astrophysics experiments. Sterile neutrinos are a hypothetical fourth kind of neutrino, which are motivated by anomalies observed in various short base-line neutrino experiments. These experiments have published results that are not mutually compatible. This thesis presents a global fit to many short base-line datasets with the addition of the recent IceCube sterile neutrino search, constraining the full 3+1 mixing matrix for the first time. The global fit strongly favours the sterile neutrino hypothesis, although significant tension still remains within the datasets. The origin of the observed astrophysical neutrino flux at IceCube remains elusive. Current methods, using a hot-spot model, have seen no significant clustering of events. This thesis presents a new test for point sources of neutrinos, based on the non-Poissonian Template Fitting technique. Constraints on population models for neutrino points sources are shown for the first time. Atmospheric neutrinos form a background for astrophysical analyses on IceCube, but also serve as the signal in particle physics analyses such as the sterile neutrino search. The first comprehensive study of the effect of global atmospheric temperature variations on atmospheric neutrino fluxes is provided. This thesis also presents two studies on using new computational methods for simulation and reconstruction on IceCube. Convolutional neural networks have been used to classify low-level waveform data, with the goal of identifying tau-neutrinos. Metropolis light transport, a rendering technique used in the CGI industry, has been extended to simulate the transport of light inside the IceCube experiment. Both show promising results, exceeding existing algorithms in their test cases. / by Gabriel L.W.H. Collin. / Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 313-328). / In this thesis, I present the realization of a system applying the tools of cavity quantum electrodynamics to an atomic optical lattice clock. We design and implement a unique experimental cavity structure, with a small radius of curvature mirror on one side and a large mirror on the other side. With this structure, we are able to probe ytterbium-171 atoms in both the weak and strong coupling regimes of cavity quantum electrodynamics. This asymmetric micromirror structure simultaneously offers strong light-atom coupling, mechanical robustness, and excellent access to a large cavity volume. We develop a simple but accurate model for strong light-atom interactions in our system, which allows us to predict the performance of both cavity-assisted quantum non demolition measurements of the atomic state, and the back-action of the probing light onto the atomic state. We find theoretically, and confirm experimentally, that probing the atom-cavity system with two frequencies at the vacuum Rabi peaks of a system with strong collective light-atom coupling generates the largest possible entanglement between the probing light and the atomic state. With this scheme, we demonstrate atomic number measurements within a factor of 2 of the quantum Fisher information limit. By using the quantum back-action of the probing light on the atomic ensemble, we perform squeezing by cavity feedback. We produce states with -11±1 dB of variance squeezing and 14±1 dB of anti squeezing. Using theoretical simulations, we show that states with near-unitary squeezing offer significant advantages for improving atomic clocks compared to previous work. The ability to load large atomic ensembles in the strong coupling regime in our system offers several routes to the generation of highly entangled non-Gaussian quantum states. Such states can be produced by heralded measurements, or by global atom-atom interactions based on unitary spin squeezing. Altogether, we realize a system of unprecedented versatility and great potential for performing a large variety of hybrid atomic clock and cavity QED experiments. / by Boris Braverman. / Ph. D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007. / Includes bibliographical references (p. 59-62). / In this thesis we designed and began the fabrication of three new solid state sensors for the detection of DNA hybridization through electrical measurements. The first sensor is a surface acoustic wave device with tapered IDTs capable of giving us a tomographic image of the functionalized sensor surface. We investigated using an array of these type sensors to produce a novel DNA sequencing platform on par with the state-of-the-art sequencing machines of today. The second sensor we designed is a quantum dot-based conduction sensor, where quantum dots in the substrate exponentially increase its conductivity when hybridization events occur. The third sensor is a HEMT AlGaN transistor where the drain access region serves as the functionalized area, so hybridization events increase the parasitic capacitance and change the switching frequency of the device. We have also identified the sensitivity limits and other relevant parameters for each of these devices. / by Ryan Taylor Sheffler. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2001. / Includes bibliographical references (leaves 38-39). / Babar is measuring the value for sin(2[beta]) in the unitary triangle of neutral Bd mesons produced in e⁺e⁻ collision. This thesis explores a model of the [gamma]T(4S) resonance created in this collision that is composed of two one-state systems instead of one two-state system. Considering only neutral mesons, I write a Monte Carlo simulation to determine an adjusted value for [Delta]m and use this value to fit the data that Babar published. Based on this analysis, I find sin(2[beta]) = .75 ± .27, about double the value that Babar measures. / by Susama Agarwala. / S.B.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1992. / Includes bibliographical references (leaves 52-53). / by David W. Hogg. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 123-124). / Understanding the phenomena of shock propagation and of turbulent mix induced by Rayleigh-Taylor (RT) instability growth is of critical importance for ignition and high gain in inertial confinement fusion (ICF). Capsule assembly and hot-spot formation require careful timing of multiple shocks to maximize hot-spot heating while minimizing heating of the main fuel. Unmitigated mixing of the main fuel with the hot-spot can quench hot-spot heating, resulting in reduced gain or failed ignition. Nuclear measurements of direct-drive implosions at the OMEGA laser facility were performed to study shock convergence and mix dynamics in ICF. During these studies, an unexpected scaling of experimental nuclear yields was observed in implosions of capsules filled with different mixtures of D2 and 3He. A number of possible mechanisms to cause the scaling were considered, but no dominant mechanism has been identified. Mix dynamics were studied using a novel capsule configuration that only emits D3He protons when the fuel and shell are atomically mixed. Temporal and spectral measurements of protons emitted from such capsules were used to investigate the extent and evolution of mix, and demonstrate that the time necessary for RT instabilities to induce mix results in a delay of the peak D3He reaction rate in these special capsules compared to standard capsules. / (cont.) The collapse of a converging spherical shock launched by the onset of the laser pulse induces nuclear production several hundred picoseconds before deceleration and stagnation of the imploding shell. The time, duration, nuclear yields, temperature, and target compression of this shock-induced burn were measured and compared to 1-D simulations. The simulations significantly overestimate the yields, time, and compression, even though the shock collapse and resulting nuclear reaction history were experimentally demonstrated to be 1-D in nature. A 1-D model of shock convergence was constructed to gain insight into the discrepancy between experiments and simulations by extending Guderley's converging shock analysis. It is hoped that the constraints imposed by these nuclear measurements of shock convergence and mix dynamics will enable useful tests to affirm the validity or improve the utility of the analytic and numerical tools used to understand these phenomena. / by James Ryan Rygg. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2008. / Includes bibliographical references (p. 69-73). / We investigate the robustness with respect to the introduction of nonconformality of five properties of strongly coupled plasmas that have been calculated in K = 4 supersymmetric Yang-Mills (SYM) theory at nonzero temperature, motivated by the goal of understanding phenomena in relativistic heavy ion collisions. (The five properties are the jet quenching parameter, the velocity dependence of screening, and the drag and transverse and longitudinal momentum diffusion coefficients for a heavy quark pulled through the plasma.) We do so using a toy model in which nonconformality is introduced via a one-parameter deformation of the AdS black hole dual to the hot KN = 4 SYM plasma. For values of this parameter which correspond to a degree of nonconformality comparable to that seen in lattice calculations of QCD thermodynamics at temperatures a few times that of the crossover to quark-gluon plasma, we find that the jet quenching parameter is affected by the nonconformality at the 30% level or less, the screening length is affected at the 20% level or less, but the drag and diffusion coefficients for a slowly moving heavy quark can be modified by as much as 80%. However, we show that all but one of the five properties that we investigate become completely insensitive to the nonconformality in the high velocity limit v --, 1. The exception is the jet quenching parameter, which is unique among the quantities that we investigate in being "infrared sensitive" even at v = 1, where it is defined. That is, it is the only high-velocity observable that we investigate which is sensitive to properties of the medium at infrared energy scales proportional to T, namely the scales where the quark-gluon plasma of QCD can be strongly coupled. The other four quantities all probe only scales that are larger than T by a factor that diverges as v -- 1, namely scales where the KN = 4 SYM plasma can be strongly coupled but the quark-gluon plasma of QCD is not. / by Yeming Shi. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student submitted PDF version of thesis. / Includes bibliographical references (p. 67-75). / In this thesis, we are investigating cosmological implications of hidden sector models which involve scalar fields that do not interact with the Standard Model gauge interactions, but couple directly to the Higgs field. We particularly focus on their relic particle density as a candidate for dark matter. For the case of hidden sector without a gauge field we have improved the accuracy of the bounds on the coupling constant and give bounds on the Lagrangian parameters. Models with Abelian and non-Abelian gauge fields are also studied with relic density bounds, BBN and galactic dynamics constraints. Several discussions on phase transitions and alternative dark matter candidates are included. / by Serkan Cabi. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1996. / Includes bibliographical references (leaves 155-160). / by Wing Yee Sunny Tam. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 65-66). / Optical links are a promising alternative to the electrical interconnects that are currently used between chips within a computer. A crucial part of an optical link is a modulator, a device that converts an electrical signal into an optical signal. This thesis explores the physics of how these modulators operate. I built a general purpose optical and electrical testing station to perform these measurements. The optical transmission spectra of the set of modulators studied had extinction ratios in the range of 5 to 27 dB, which is sufficient for modulation. I developed analytical and T-Matrix models to extract physical parameters from the transmission scans, such as light transmission, loss in the ring, and index of refraction of the contact section. The modulators worked with an open eye up to frequencies of 600 MHz. A theoretical model was developed to match the data and experiment with injection and recombination dynamics. Finally, several design solutions are suggested to further improve the modulators and to move towards the goal of modulators that operate at 5 Gb/s. / by Matthew J. Weaver. / S.B.