Thesis (M.Sc.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2008/12/07). Includes bibliographical references.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Howard Baer, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Jan. 27, 2005). Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 1993.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Paul R. Shapiro. Vita. Includes bibliographical references.

abstract: The identity and origin of dark matter is one of the more elusive mysteries in the fields of particle physics and cosmology. In the near future, direct dark matter detectors will offer a chance at observing dark matter non-gravitationally for the first time. In this thesis, formalisms are developed to analyze direct detection experiments and to quantify the extent to which properties of the dark matter can be determined. A range of non-standard assumptions about the dark matter are considered, including inelastic scattering, isospin violation and momentum dependent scattering. Bayesian inference is applied to realistic detector configurations to evaluate parameter estimation and model selection ability. A complete set of simplified models for spin-0, spin-1/2 and spin-1 dark matter candidates are formulated. The corresponding non-relativistic operators are found, and are used to derive observational signals for the simplified models. The ability to discern these simplified models with direct detection experiments is demonstrated. In the near future direct dark matter detectors will be sensitive to coherent neutrino scattering, which will limit the discovery potential of these experiments. It was found that eleven of the fourteen non-relativistic operators considered produce signals distinct from coherent scattering, and thus the neutrino background does not greatly affect the discovery potential in these cases. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

Observations from a broad range of astrophysical scales have forced us to the realization that the well understood matter comprising the stars and galaxies we see around us accounts for only a small fraction of the total mass of the Universe. An amount roughly five times larger exist in the form of dark matter about which we have virtually no direct evidence apart from its large scale gravitational effects. It is also known that the largest contribution to the energy density of the universe is the dark energy, a negative pressure form of energy which will not be dealt with here. I will present a candidate for the dark matter which is based completely in known physics and which presents several possible observational signatures. In this model the dark matter is composed of dense nuggets of baryonic matter and antimatter in a colour superconducting state. If these object are sufficiently massive their low number density will make them effectively dark in the sense that collisions with visible matter become infrequent. This work presents the basics of dark matter as a colour superconductor and then uses the physical properties of the quark nuggets to extract observational consequences. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Hidden sector or dark sector states appear in many extensions to the Standard Model (SM), to provide particle mediators for dark matter in the universe or to explain astrophysical observations such as the positron excess in the cosmic microwave background radiation flux. A hidden or dark sector can be introduced with an additional U(1)d dark gauge symmetry. The discovery of the Higgs boson in 2012 during Run 1 by the Large Hadron Collider (ATLAS and CMS) opens a new and rich experimental program for Beyond Standard Model physics (BSM) based on the Higgs Portal. This exotic discovery route uses couplings to the dark sector at the Higgs level, which were not experimentally accessible before. This thesis presents the searches of possible exotic decays: H → ZdZ(d) → 4` where Zd is a dark vector boson. It had been initiated in the Run 1 period of the LHC using the ATLAS detector at CERN. The results showed (tantalizingly) two signal events where none were expected, so that in the strict criteria of High Energy Physics, the result was not yet statistically significant. The Run 1 analysis for a 8 TeV collision energy is further developed in Run 2 with a 13 TeV collision energy, to expand the search area, take advantage of higher statistics, a higher Higgs production cross section, and substantially better performance of the ATLAS detector. In this work, the search is further broadened and includes allowing the mass of the originating boson (the dark Higgs S) to vary from the SM value. This allows the search for the dark vector boson to also explore higher or lighter masses than the SM Higgs boson. This extended search is efficient and could include a more general class of models, with the mass constraint of the SM Higgs portal lifted. This thesis reviews the analysis results from Run 1 and Run 2, and presents its iteration in the full Run 2 search by focusing on its new channel where the additional scalar S (with mS 6= mH) decays to 4` via two dark vector boson states Zd . The case where the Higgs decays to 4` via two Zd (H → ZdZd → 4`) and also called high mass channel, has been just unblinded. Nineteen data events are observed where 14 were predicted. In overall, the data are consistent with the Monte Carlo prediction. No evidence of deviation from the Standard Model expectations are observed. / College of Engineering, Science and Technology / Ph. D. (Physics)

Thesis (Ph.D.)--Boston University / The existence of Dark Matter was first proposed by Fritz Zwicky in 1933, based on the observed velocity distribution of galaxies in the Coma Cluster. Subsequent studies of visible mass and velocity distributions in other galaxies have confirmed Zwicky's original observation; there is now little doubt that Dark Matter exists. However, due to the fact that Dark Matter interacts very weakly through non-gravitational forces, nothing is known about the nature of Dark Matter. It is believed that Dark Matter particles are streaming toward the Earth, in the Earth's rest frame, from the direction of the constellation Cygnus. Observation of this so-called Dark Matter 'wind' with a direction-sensitive dark matter particle detector would be compelling evidence that Dark Matter does consist of a gas of discrete particles as a new form of matter. The DMTPC collaboration is developing such a detector, and this thesis describes R&D work in support of that project. The DMTPC technique for looking for Dark Matter relies on Dark Matter particles interacting with atomic nuclei, causing the nuclei to recoil and to leave optical signals that can be detected. Since neutrons are electrically neutral and collide with nuclei, they can mimic Dark Matter signals. Therefore, the reduction of neutron background is critical to the successful detection and identification of Dark Matter particles. One important aspect of this thesis is to fully understand and quantify neutron interactions with our detector. In addition to providing information for understanding Dark Matter experiments, this work also allows us to understand how our device can be used as a neutron detector. We have been able to measure a number of neutron events in a variety of experimental runs both with and without neutron sources such as a neutron generator and 252 Cf. From these runs, we have obtained data for both elastic and inelastic interactions of neutrons of various energy ranges with detector gas nuclei. In this thesis, I will also discuss our current background data taking for the Dark Matter research and our plan for scaling up the detector to 100 m 3 for a competitive Dark Matter search.

No description available.

The cubic-kilometer sized IceCube neutrino observatory, constructed in the glacial ice at the South Pole, searches indirectly for dark matter via neutrinos from dark matter self-annihilations. It has a high discovery potential through striking signatures. This thesis presents searches for dark matter annihilations in the center of the Sun using experimental data collected with IceCube. The main physics analysis described here was performed for dark matter in the form of weakly interacting massive particles (WIMPs) with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore sub-array was included in the analysis, lowering the energy threshold and extending the search to the austral summer. Data from 317 days live-time are consistent with the expected background from atmospheric muons and neutrinos. Upper limits were set on the dark matter annihilation rate, with conversions to limits on the WIMP-proton scattering cross section, which initiates the WIMP capture process in the Sun.These are the most stringent spin-dependent WIMP-proton cross-sections limits to date above 35 GeV for most WIMP models. In addition, a formalism for quickly and directly comparing event-level IceCube data with arbitrary annihilation spectra in detailed model scans, considering not only total event counts but also event directions and energy estimators, is presented. Two analyses were made that show an application of this formalism to both model exclusion and parameter estimation in models of supersymmetry. An analysis was also conducted that extended for the first time indirect dark matter searches with neutrinos using IceCube data, to an alternative dark matter candidate, Kaluza-Klein particles, arising from theories with extra space-time dimensions. The methods developed for the solar dark matter search were applied to look for neutrino emission during a flare of the Crab Nebula in 2010.