# Alumni

Degree Date: May, 2013

John Murray
Xiao-Jing Wang

# Specialization of neural circuits for cognition: linking structure to function through dynamics

The brain achieves flexible cognition through specialization of cortical areas for different functions. To subserve working memory, prefrontal cortex can maintain a persistent pattern of activity in the absence of a stimulus, whereas sensory areas do not. What is the neural circuit basis of specialized function? Strong recurrent structure in synaptic connections endows a circuit with attractor dynamics that can subserve cognitive function. This suggests that areas achieve specialization in part... more

Richard Wall
Paul Tipton

# A study of heavy flavor quarks produced in association with top quark pair events at sqrt(s) = 7 TeV using the ATLAS detector

In this thesis, we show evidence for the production of ttbar + b + X and ttbar + c + X, together refered to as ttbar + HF, at the Large Hadron Collider. A sample of dilepton ttbar candidate events with three or more b-tagged jets is used to isolate a $\ttbar$ sample rich in extra heavy flavor jets. A fit to the vertex mass distribution for the b-tagged jets in this region is performed to extract the flavor composition of the additional b-tags. This measurement is converted to a cross-section... more

Brian Walsh
Tobias Golling

# SEARCH FOR STOP SQUARK PAIR PRODUCTION IN FINAL STATES WITH ONE ISOLATED LEPTON, JETS, AND MISSING TRANSVERSE MOMENTUM IN SQRT(S) = 7 TeV COLLISIONS USING 4.7 fb^(-1) OF ATLAS DATA

A cut-and-count search for stop squark pair production in pp collisions at √s = 7 TeVwith 4.71 fb−1 of 2011 ATLAS data is presented. Events with one isolated lepton, four or more jets, and missing transverse energy are selected to study a simplified model of stop squark decay to one top quark and one neutralino χ ̃01. Data is seen to be compatible with Standard Model-only hypothesis, and model-dependent as well as model-independent exclusion limits are set.
Degree Date: December, 2012

Steven Eckel
Steve Lamoreaux

# A Search for the Electron EDM using Europium-Barium Titanates

The discovery of a permanent electric dipole moment (EDM) of a fundamental particle would prove a great discovery in modern physics, as such an EDM would violate some of the core symmetries of the fundamental forces of nature. Many models that go beyond the standard model of particle physics produce EDMs with magnitudes approaching the level detectable by the next generation of experiments. One possibility for such an experiment involves the use of a solid sample at low temperatures. In a... more

Matthew Phillips
Gordon M. Shepherd

# Sensory Processing in the Olfactory Bulb: From Lateral Inhibition to Behavior

Sensory perception is the fundamental process by which all organisms gain knowledge of their world. Perceptions arise from stimulations of sensory receptors that are translated into neuronal signals. These signals become processed and refined greatly before reaching conscious awareness in higher brain areas. Understanding the mechanisms and functions of this processing is a significant and major challenge for science. The use of model systems, such as the mammalian olfactory system, is helpful... more

Hasuk Francis Song
Karyn Le Hur

# Entanglement in Quantum Many-Body Systems

The scaling of entanglement entropy and, more recently, the full entanglement spectrum have become useful tools for characterizing certain universal features of quantum many-body systems. We motivate the importance of entanglement in the study of many-body systems by considering the “gratuitously big” size of Hilbert space and the need for generic ansatzes that efficiently represent useful wave functions. In addition, we study the scaling of the entanglement entropy in the two-... more
Degree Date: May, 2012

Hanghui Chen
Sohrab Ismail-Beigi

# A first principles study of oxide interfaces

Both theoretically and experimentally, enormous progress has been made toward understanding and controlling materials at the atomic scales. The advances in thin film deposition techniques make it possible to grow artificially designed heterostructures that do not exist in nature. The theoretical developments of ab initio calculations combined with the rapid increase of computational capability enable scientists to analyse data, make predictions and even design experiments from numerical... more

Andrew Jayich
Jack Harris

# Laser cooling a 261 kHz harmonic oscillator

Optomechanics is a diverse field where mechanical harmonic oscillators are coupled to an optical field via radiation pressure. The mechanical devices range from atom clouds and nanotubes up to the kilogram scale mirrors used in the LIGO observatories. The starting point for many interesting measurements begins with the mechanical device in its ground state, where it has less than a phonon worth of energy. In Jack Harris's lab we are working to cool a mechanical membrane to its ground state... more

Benjamin Kaplan
Paul L. Tipton

# Testing the Standard Model of Particle Physics: A Search for New Phenomena in Multilepton Events with the ATLAS detector at the LHC

An excess of events over the Standard Model predictions in final states with three or more high momentum charged leptons would constitute evidence of new physical processes. Presented is a generic search for new phenomena in such events. To reduce the largest Standard Model backgrounds, events consistent with the production of a Z boson are rejected. Events are selected from 1.02 fb$^{-1}$ of proton-proton collision data recorded by the ATLAS detector at $\sqrt{s}$ = 7 TeV. There is no... more

Sarah Lockwitz
Paul Tipton

# A Search for the Standard Model Higgs Boson in CDF II Data

This dissertation presents a search for the standard model Higgs boson in the associated production process proton anti-proton to ZH to electron positron b quark anti-b quark. Data amounting to an integrated luminosity of 7.5/fb at a center of mass energy of 1.96 TeV collected at the Collider Detector at Fermilab (CDF) at the Tevatron are analyzed. Two objectives are pursued in the methods applied: maximize acceptance, and distinguish the signal from background. The first aim is met by applying... more

Michel Devoret

# Superinductance: a New Element for Quantum Circuits

No abstract available

Carl Schreck
Corey O'Hern

# Mechanical and vibrational properties of model granular media

This thesis describes comprehensive computational and theoretical studies of the mechanical and vibrational properties of athermal particulate systems, such as granular media, foams, and emulsions, modeled as frictionless particles with spherical or ellipsoidal shapes. First, we investigate the mechanical properties of static packings of ellipsoidal particles. While amorphous packings of spherical particles are isostatic at jamming onset and possess the minimum contact number $z=z_{\rm iso}$... more

Benjamin Zwickl
Jack Harris

# Progress Toward Observation of Radiation Pressure Shot Noise

Abstract: It has been over 100 years since the first conclusive demonstration of radiation pressure by Lebedev and Nichols and Hull. Cavity optomechanical systems---high finesse optical cavities coupled to mechanical resonators---are good testing grounds for the mechanical properties of light. The system described in this dissertation is a 7 mm long cavity coupled to a 1 mm square, 50 nm thick silicon nitride membrane. Like many similar optomechanical systems, ranging from LIGO to microtoroids... more
Degree Date: December, 2009

Ke Han
Jack Sandweiss

# Search for Stable Strange Quark Matter in Lunar Soil

Strange Quark Matter (SQM) is a proposed state of hadronic matter made up of roughly one-third each of up, down, and strange quarks in a single hadronic bag. For the last three decades, a wide range of experimental searches for strangelets (small lumps of SQM with baryon number less than 106) have been conducted but all failed to give a definite answer to the existence of SQM. We report results from a search for strangelets in a lunar soil sample, in which the predicted strangelet concentration... more
Degree Date: May, 2008

Yong Jiang
David DeMille

# Progress Towards Searching for Electron Electric Dipole Moment Using PbO

Observation of a non-zero electron electric dipole moment (EDM) will be explicit evidence for physics beyond the Standard Model. There is significant interest in developing experiments that can probe beyond the current limits for the electron EDM. An experiment to look for the EDM of the electron using the metastable a(1) [3Σ+] state of the PbO molecule has been implemented at Yale University. We populate the a(1) [3Σ+] state of 208PbO using laser-microwave double resonance, and we... more