Degree Date: May, 2015

Emma Ideal
Sarah Demers

A Search for the Standard Model Higgs Boson Produced in Association with a Vector Boson and Decaying to a Hadronically-Decaying Tau Pair at ATLAS

On July 4, 2012, the discovery of the Higgs boson was simultaneously announced by the ATLAS and CMS collaborations. Since then, evidence for its decay to tau leptons has been claimed. As of now, there have been no Higgs discoveries in any of its associated production modes. For this thesis, a search for the Higgs boson produced in association with a vector boson V = W^(+-), Z and decaying to a tau lepton pair was conducted using 2012 ATLAS data. The data corresponds to 20.3 fb^(-1) of 8 TeV... more

Andrew Leister
Sarah Demers

A Search for Z' Gauge Bosons Decaying to Tau-Antitau Pairs in Proton-Proton Collisions with the ATLAS Detector

Although the Standard Model of Particle Physics has been generally successful in modeling fundamental particles and their interactions, it does not incorporate many observed physical phenomena. Many theoretical models attempting to explain physics beyond the Standard Model have been developed, several of which include one or more additional neutral gauge bosons, or Z'. The potential mass range of a Z' is quite large and for some models includes Z' masses at the TeV scale. A search... more

Christopher McKitterick
Daniel Prober

Prospects for Ultra-sensitive Terahertz Photon Detection with Graphene

This dissertation investigates a new scheme for the detection of terahertz (THz) photons. The vast majority of photons visible to outer space observatories occur in the far-infrared, but there do not yet exist detectors sensitive enough to accurately measure the faintest signals. I propose to use graphene, a single atomic layer of graphite, as the detecting element to observe these weak sources. As a result of its nano-scale dimensions, there are few charge carriers in graphene systems per unit... more

Xiaoxiao Wang
Tobias Golling

Search for a supersymmetric partner of the top quark using boosted top quark identification with the ATLAS detector

The Higgs discovery at the LHC has brought new attention to the hierarchy problem and the theory of Supersymmetry (SUSY). The supersymmetric partner of the top quark - the top squark (stop), is of paramount importance as it contributes the largest higher-order radiative corrections to the Higgs squared-mass. Naturalness arguments favor a light stop, making it a good candidate for discovery at the LHC. A search of the stop pair production in final states with one isolated lepton, jets, and... more
Degree Date: December, 2014

Ana Malagon
O. Keith Baker

Search for 140 microeV Pseudoscalar and Vector Dark Matter Using Microwave Cavities

Dark matter plays an important role in structure formation and composes 26.8% of the total energy density in the universe. There are many postulated particles that are theorized to be the constituents of cold dark matter; however, none have been observed experimentally. One strongly motivated particle that could be cold dark matter is the axion, a pseudoscalar with a two photon vertex. Experimental techniques to detect dark matter axions rely on a multiphoton radiative transition; in the... more

Gennady Voronov
George Fleming

The Extent of the Two-Color Fundamental Conformal Window

The $SU\!\left(2\right)$ gauge theories with $N_{f}$ flavors of massless vector-like Dirac fermions transforming in the pseudo-real fundamental representation have an enhanced global chiral symmetry and a distinct symmetry breaking pattern. These theories are expected to be qualitatively different from quantum chromodynamics (QCD) in the infrared (IR), especially with respect to the properties of the Nambu-Goldstone bosons (NGB). Having the potential to elucidate many features of both known and... more

Liyao Wang
Mokshay Madiman

Heat capacity bound, energy fluctuations and convexity

In classical statistical mechanics, the heuristic that in the canonical ensemble the energy distribution is sharply peaked at the mean energy is crucial in justifying the equivalence between the canonical and microcanonical ensembles. It turns out that this is closely related with the fundamental notion of a typical set and the Shannon-McMillan-Breiman theorem in information theory. In this dissertation, we explore the connections between the two and establish some new rigorous results that are... more
Degree Date: May, 2014

Colin Bruzewicz
David DeMille

Continuous Optical Production of Ultracold Vibronic Ground State Polar Molecules

Polar molecules present an exciting new test bed for ultracold physics with applications in numerous fields, such as chemical reaction dynamics, many-body systems, and quantum computation. Creating large samples of these molecules that can be trapped for long times, however, remains an ongoing challenge. We demonstrate the direct formation of vibronic ground state RbCs molecules by photoassociation of ultracold atoms followed by radiative stabilization. From analysis of the relevant free-to-... more

Bernard Hicks
Helen Caines

Differential Production Cross-Section of Heavy-Flavor Electrons in √s = 2.76 TeV pp collisions at the LHC with the ALICE detector

Recent results at RHIC seem to confirm T.D.Lee’s hypothesis that a new form of matter, the quark- gluon plasma (QGP), could be formed in heavy-ion collisions at high energies. Heavy quarks, being formed in the early stages of heavy-ion collisions, form a good probe for the properties of the QGP. The energy loss of heavy quarks as they traverse the medium is predicted to be less than that of the lighter quarks. However, previous measurements of the nuclear modification factor at RHIC... more

Lawrence Lee
Tobias Golling

A Search for B-violating Supersymmetry in Multijet Signatures at the ATLAS Experiment

With supersymmetry (SUSY) increasingly constrained, more attention is placed on alternate flavors of SUSY that allow for an unexcluded natural theory. A search for new physics phenomena in all-hadronic signatures in \sqrt{s}=8 TeV pp collisions using an integrated luminosity of 20.3 fb^-1 collected by the ATLAS detector at the LHC will be presented. Within the context of SUSY, gluino pair-production gives rise to multijet final states in models that allow for violation of R-parity. Two types of... more

Rongrong Ma
John Harris

Jet measurements in pp and Pb-Pb collisions in ALICE

Lattice-QCD predicts the existence of a new form of hot, dense matter called the Quark Gluon Plasma (QGP) above a critical energy density. Such matter is believed to be created in relativistic heavy-ion collisions, where sufficient energy is expected to be deposited by colliding ions in a limited volume. To study the properties of the QGP, high transverse momentum (pT) partons produced at the early stage of the collisions are used as probes. Since partons are not directly measurable, jet... more

Tianqi Shen
Corey O'Hern

Contact Percolation, Fragility and Frictional Packings

This thesis presents four computational and theoretical studies of the structural, mechanical, and vibrational  properties of purely repulsive  disks, dimer-, and ellipse-shaped particles with and without friction.  The first study investigated the formation of interparticle contact networks below jamming onset at packing fraction φJ , where the pressure of the system becomes nonzero.  We generated ensembles of static packings of frictionless disks over a range of... more
Degree Date: December, 2013

John Barry
David DeMille

Laser cooling and slowing of a diatomic molecule

Laser cooling and trapping are central to modern atomic physics. It has been roughly three decades since laser cooling techniques produced ultracold atoms, leading to rapid advances in a vast array of fields and a number of Nobel prizes. Prior to the work presented in this thesis, laser cooling had not yet been extended to molecules because of their complex internal structure. However, this complexity makes molecules potentially useful for a wide range of applications. The first direct laser... more

Prasenjit Dutt
R. Shankar

Strongly correlated quantum transport out-of-equilibrium

The revolutionary advances in nanotechnology have facilitated the precise control and manipulation of mesoscopic systems where quantum effects are pronounced. Typical experimental settings are capable of driving these systems far from equilibrium, where linear response theory is inadequate. We study transport through quantum-impurity systems in the regime of strong correlations and determine the effects of large temperature and potential gradients on its many-body physics. We introduce a... more

Merideth Frey
Sean Barrett

Using Novel Pulse Sequences for Magnetic Resonance Imaging of Phosphorus-31 in Hard and Soft Solids

Since its invention in 1973, magnetic resonance imaging (MRI) has become an invaluable tool for clinical medicine, fundamental biomedical research, the physical sciences, and engineering. The vast majority of all MRI studies, in medicine and beyond, detect only the signal from a single nuclear isotope, H-1, in liquid water. Extending the reach of MRI to the study of other elements, and to hard or soft solids, opens new frontiers of discovery. In practice, however, the slower motion of the... more