University of Washington

Seattle, Washington

2000 UW REU Program in Physics

Research Projects

The projects and groups listed below are intended to provide interested students with an overview of research offerings in the Department of Physics, University of Washington. The list is not inclusive, but it is representative of the breadth of research opportunities within the Physics Department and INT. Students with particular interests should feel free to ask Wick or Martin whether special projects can be designed: we have done this in past years with good success.


NUCLEAR PHYSICS LABORATORY

Testing the Equivalence Principle using a High-Precision Torsion Balance
Faculty: Eric Adelberger, Jens Gundlach, Blayne Heckel

The Eot-Wash group is building a new instrument to make the world's most precise test of Einstein's equivalence principle which says that gravitation is equivalent to an acceleration of the coordinate frame and is the underpinning of general relativity. You can find out more about this by clicking on the Eot-Wash research group on the University of Washington Physics Department home page on the Web. We have several interesting technical projects suitable for experimentally inclined summer students. Our lab is well equipped with instrumentation, machine and electronic shops so that plenty of resources are available for attacking these problems. Two examples are:
1) developing a higher performance optical system for reading out the twist of the torsion balance
2) developing an actively controlled temperature-regulation system for the torsion balance. We currently hold the temperature constant to a few millidegrees and want to do better.
3) testing the noise performance of torsion fibers made of different materials.

Millimeter-scale Tests of Inverse-square Law and Other Precision Tests of Gravitational Physics
Faculty: Eric Adelberger, Blayne Heckel, Jens Gundlach, Steve Merkowitz, and Ulrich Schmidt

The Eot-Wash group has begun a new project to test an exciting prediction that Newton's inverse-square law could break down at the millimeter scale. If verified experimentally, this prediction would provide strong evidence for more than 3+1 dimensions, i.e. that some of the "extra dimensions" of modern theories could have detectable consequences. Our experiment employs a novel torsion balance and attractor whose design was optimized by 2 REU students from last year's program.

We are also continuing to improve the torsion balance instruments used in our tests of Einstein's Equivalence Principle. These instruments, which currently yield the most precise tests of this important physical principle, are continuously being upgraded and provide many interesting projects for technically inclined students. Our lab is well equipped with instrumentation, machine and electronic shops so that plenty of resources are available for attacking these problems.

You can learn more about our group by clicking on the Eot-Wash research group on the University of Washington Physics Department home page.

The Sudbury Neutrino Observatory
Faculty: Peter Doe, Steve Elliott, Hamish Robertson, Tom Stieger, John Wilkerson

The Sudbury Neutrino Observatory (SNO) is a massive, heavy water Cerenkov detector in operation 2 km underground in Sudbury, Ontario. SNO's main research thrust is the study of solar neutrinos, but it is also sensitive to atmospheric neutrinos as well as neutrinos emitted from nearby (galactic) supernova. Using its unique neutrino flavor detection capabilities, SNO hopes to provide a definitive resolution of the long standing "solar neutrino problem", where all existing experiments observe fewer neutrinos from the sun than predicted by theory. Current explanations of the problem favor the existence of new neutrino properties such as neutrino mass and the violation of lepton family number. Work at UW in the summer of 2000 by our group (5 Faculty, 1 postdoctoral fellow, 8 graduate students) will concentrate on the operation of the detector system, analysis of the data being collected, and final preparation of a neutron detector system that will be used by SNO to make the key measurement of neutral-current neutrino interactions. There are numerous interesting research opportunities available. More information on SNO, plus other useful links can be found at our web site: http://EWIServer.npl.washington.edu/sno/sno.html

Weak Interactions, Symmetries, and Neutrinos
Faculty: Peter Doe, Steve Elliott, Hamish Robertson, Tom Steiger, and John Wilkerson

In addition to SNO, our group is involved in a number of projects probing the weak interaction and neutrino properties. Current projects underway include emiT, a precision neutron beta decay measurement that is testing time-reversal invariance, as well as SAGE, the Russian American Gallium Experiment. On SAGE we are involved in the analysis of data from this gallium based solar neutrino experiment (an experiment sensitive to the low-energy p-p fusion neutrinos). We are also investigating an idea for using Pb as a target in a new neutrino-oscillation search at an accelerator. The Pb nucleus has a relatively large cross section for neutrino interactions. An REU student is encouraged to consider working with us in any of these areas. More details of the research activities of the Electroweak Interactions Group are available at: http://EWIServer.npl.washington.edu .

The Washington Large Area Time Coincidence Array
Faculty: John Cramer, Peter Doe, Steve Elliott, John Wilkerson, Jeff Wilkes

We propose to construct the Washington Large Area Time Coincidence Array (WALTA), an extended network of cosmic ray shower detectors, the elements of which will be placed in Washington area high schools. The primary functions of this network are physics education outreach and investigation of ultra High energy cosmic rays, the existence of which is one of the major unsolved problems of contemporary astrophysics. Work at UW in the summer of 2000 will include computer simulation of the response of the array to ultra high energy cosmic rays, prototyping an individual array element and characterizing its response to cosmic rays. An REU student would be a welcome participant in any of these activities. http://www.phys.washington.edu/~walta

Super-Kamiokande and K2K: Neutrino Oscillations Studies
Faculty: Jeff Wilkes and Steve Boyd

The Super-Kamiokande underground neutrino detector reported evidence for neutrino oscillations in 1998, and last year the K2K (KEK to Kamioka) long-baseline experiment began taking data with a high-purity muon neutrino beam, directed from a near detector site at KEK through the earth to Super-K. Students will have an opportunity to help on any of a wide variety of data analysis topics relating to these projects. Also, we will be preparing hardware for the planned Super-K upgrade in 2001.

Measurement of the Reaction Rate for Producing Energetic Neutrinos in the Sun
Faculty: Kurt Snover, Tom Steiger, Arnd Junghans, Eric Adelberger

The "solar neutrino puzzle," one of the current major puzzles in physics, consists of the observation that many fewer neutrinos from the sun are detected here on earth than are expected based on solar model calculations. We have recently developed the apparatus and techniques for a new measurement of the reaction rate for the fusion of 7Be with low energy protons, producing 8B. The decay of 8B in the Sun is the source of high energy neutrinos, and this reaction rate is a crucial ingredient in the model calculations. Reaction rate measurements will be taking place this summer. An interested REU student is welcome to join us and participate in any phase of the measurement and its interpretation.

EARLY UNIVERSE COSMOLOGY

Baryogenesis: Why the universe is made of matter
Faculty: Ann Nelson

According to standard Big Bang cosmology, the very early universe contained nearly equal amounts of matter and antimatter, with 10⁸ antiquarks. Such a tiny asymmetry can be explained and computed if at still earlier times, the universe was completely symmetric under matter-antimatter interchange, and the cosmological asymmetry evolved as a result of a tiny asymmetry in the fundamental laws of physics. Creating a net matter-antimatter asymmetry from symmetric initial conditions is known as baryogenesis.

In supersymmetric theories, baryogenesis is possible through the classical evolution of the scalar fields associated with the superpartners of the quarks. Study of this process involves numerical solution of nonlinear ordinary differential equations and should be quite feasible for an advanced undergraduate.

ASTROPHYSICS

Planetesimal Dynamics
Faculty: Derek Richardson, Tom Quinn, George Lake

From planet formation to planetary rings, from fragile comets and asteroids to sandpiles, there is a large diversity of problems related to planetary science that can be addressed with numerical simulations. For example, the surprising configurations of planetary systems recently discovered around nearby stars imply that planets can undergo large-scale radial motions during their formation. It is known that planetesimal scattering can cause a planet's orbit to shrink and circularize, but numerical simulations are needed to quantify this process for various disk parameters. As a different example, the spectacular breakup of Comet Shoemaker-Levy 9 and measurements of remarkably low bulk densities in some asteroids imply that small bodies in our Solar System may not be solid monoliths as we once thought. Numerical simulations reveal how these fragile bodies evolve but there are many parameters to explore. At even smaller scales, there are interesting topics in granular dynamics to investigate, such as self-organized criticality in sandpiles. The chosen project would provide experience performing simulations with sophisticated numerical code on a cluster of workstations and carrying out some analysis and visualization. We invite one REU student to join us in this effort. For more information, visit www-hpcc.astro.washington.edu/faculty/dcr or email dcr@astro.washington.edu.

CONDENSED MATTER EXPERIMENT

Dynamics at Ice Surfaces
Faculty: Sam Fain

The environment of molecules of a given material near an interface is different from that of molecules in the bulk of the material, due to bonds missing at the interface. Thus the structure and dynamics near an interface can be quite different than in the bulk. Water ice is important in a number of environments on the earth, in the atmosphere, on comets and planetary satellites, and in space. Our work on contact mode to obtain nanomechanical properties of vapor deposited ice and thickness in a controlled environment for temperatures between 250K and 273K. The fundamental information obtained by such measurements will aid in understanding the forces between ice surfaces and other solids such as occur in the adhesion of ice to objects in a cold environment on earth. An undergraduate student in Summer 2000 could assist in these experiments, learning more about both ice interfaces as well as the technique of AFM. For more information, see http://faculty.washington.edu/fain.

Physics of Thin Films
Faculty: Oscar E. Vilches

Our Low Temperature Physics laboratory is dedicated to the study of the phases of and phase transitions in very thin (one to a few atomic layers) films of simple gases on various surfaces. The goal is to understand the behavior of matter in quasi-two dimensions, particularly as to the importance of quantum effects on dimensionality. To make films of the various isotopic forms of He atoms and Hydrogen molecules, temperatures have to be reduced below 30K, while to study films of molecular nitrogen, methane, or Ar atoms temperatures can be in the liquid nitrogen temperature range. The laboratory is equipped with instrumentation to work below 1K (a dilution refrigerator), a cryostat to work above 1K using liquid helium, and small adaptable cryostats for work above 4K. Projects for Summer 2000 may involve joining graduate students studying mixtures of Helium 3 and Helium 4 below 1K adsorbed on graphite, hydrogen or deuterium molecules above 4K adsorbed on graphite or carbon nanotubes, nitrogen and/or methane adsorption on carbon nanotubes, hydrogen adsorption on gold, or Ar adsorption in silica particles. Three graduate and two undergraduate students are working currently on various projects related to the topics above. REU students have worked at the lab for three of the past four summers (1996, 98, and 99).

The Structure and Physical Properties of Disordered Materials: Sandpiles, Membranes, and Dinosaur Bones
Faculty: Jerry Seidler

The advent of the third generation synchrotron x-ray sources has provided experimentalists with x-ray beams of unprecedented intensity and collimation. One technique especially enhanced by these new beam characteristics is microtomography, more commonly known as computerized axial tomography or CAT scans. Recent technological advances have pushed the spatial resolution of 3-d microtomography down to 100nm. Our group is using microtomography to study the full 3-d structure of disordered materials such as crumpled membranes, granular bends (sandpiles), and recent and paleontological bone. These data are being analyzed in the context of statistical mechanical theories relating the effective physical properties of materials to the material's high-order structural correlation functions. Such an approach is one of the few first-principles approach to the intelligent design of materials, but has not previously been investigated in detail experimentally. The interested student would assist in studying the following questions: "How to reliably predict its physical properties?" This will involve software projects on data analysis and monte carlo simulations of disordered materials. Good knowledge of a programming language is required. Some of our group's tomography data can be viewed at: http://www.phys.washington.edu/~seidler/sand and http://www.phys.washington.edu/~seidler/bone.

CONDENSED MATTER THEORY

Computer Simulations of Excited State Electronic Structure
Faculty: John J. Rehr, A.L. Ankudinov

While density functional calculations of ground state electronic structure are now well developed, as recognized by the 1999 Nobel Prize, calculations of excited state properties and response functions are much less developed. Our group is especially interested in ab initio calculations of high energy excitation spectra, as measured by synchrotron x-ray sources. Improved numerical algorithms, e.g., for parallel computers and faster matrix inversion are needed to speed up the calculations.

ATOMIC PHYSICS

Atomic Tests of Parity Nonconservation and Time Reversal Symmetry
Faculty: Norval Fortson, Blayne Heckel, Michael Romalis

Students will be able to work directly on small scale atomic physics experiments that probe the elementary particle physics frontier. In one type of experiment, the electroweak force between electrons and quarks inside atoms is measured by the small degree of left-right asymmetry displayed by these atoms. In another type, a permanent electric dipole of an atom is being looked for as evidence of forces that distinguish between forward and backward in time. Other experiments include laser trapping of Yb atoms and applications of atomic magnetometers to biological measurements. In these experiments students can use and develop high precision lasers, ion traps, laser cooling techniques, and other tools of modern atomic physics.

Precision Measurements on Single Trapped, Laser-Cooled ions
Faculty: Hans Dehmelt, Justin Torgerson, Warren Nagourney

We work entirely with single atomic ions at rest in space. The ions are stored for long periods (up to a month) in an electrodynamic ion trap and are brought to rest using the radiation pressure of a laser beam. By studying essentially motionless ions in such pristine isolation, extremely precise measurements can be made. One application being vigorously pursued is the construction of a single-ion optical frequency standard. An atomic clock based upon such a standard could have an accuracy of one part in 10¹⁸ (or about one second in the lifetime of the universe). REU students can help with the myriad mechanical, optical and electronic tasks needed to bring these experiments to fruition. Since certain single ions can be seen with the slightly aided human eye (aided by a simple microscope), the interested student can experience an intimate connection with atomic matter not available in most other disciplines.

Cryogenic Amplifier Development for the UW Ion-trap Mass Spectrometer
Faculty: Robert Van Dyck, Jr.

Our research group conducts mass-spectroscopic measurements on single isolated ions and leptons, and at present, we have the world's most precise such spectrometer. However, in order to detect the tiny signal from the motion of a single charged particle, we need a very sensitive semi-conductor amplifier which is immersed in liquid helium. At these low temperatures (near absolute zero), ordinary silicon transistors do not work. A suitably interested REU student will be able to help reevaluate and redesign this front-end amplifier. This involves testing Gallium-Arsenide transistors (a special calss of semi-conductor devices often used in wireless communication) at cryogenic temperatures in order to find out which of the latest devices work well in our experiment. This evaluation will possibly include measuring device gain and input impedance and in determining relative stability for a wide range of frequencies.

PHYSICS EDUCATION GROUP

Instructional Strategies for Teaching Physics
Faculty: Lillian C. McDermott, Paula Heron, Peter Shaffer, Stamatis Vokos

The Physics Education Group conducts research on student understanding of physics and uses the results of this research to guide the design of instructional materials. REU participants will have the opportunity to participate in programs shaped by the group's research, such as the summer program for K-12 teachers and the tutorials for the introductory physics course. In addition to taking part in classroom activities, previous REU participants assisted in investigations of the effect of different instructional strategies on student understanding of important fundamental concepts by analyzing student performance on qualitative questions before and after instruction.

EXPERIMENTAL PARTICLE PHYSICS

Muon tube Quality Control and Monitoring
Faculty: Henry Lubatti

We are responsible for constructing a large number of proportional drift tubes that will form a precision muon detector for the LHC ATLAS experiment. The wires in the tubes must be very precisely positioned, and their tensions be within strict limits. The student would be involved in managing the system that performs these quality checks, taking the actual measurements, and managing the associated data base.

D0 Muon Chamber Commissioning
Faculty: Henry Lubatti

For students willing to spend some time at Fermilab, we have lead responsibility for the installation and commissioning of the D0 muon detectors. Under the supervision of physicists, students would help mount the chambers, connect and verify gas flow, apply high voltage and signal processing cables, and perform cosmic-ray tests. The teachers would be expected to learn about muon properties, such as lifetime.

D0 Level 3 trigger
Faculty: Gordon Watts

UW has a primary responsibility for the command and control software for the D0 Level 3 trigger system. To participate, the student must have some computer programming experience. There will be many parts to which a person with even moderate experience could contribute, involving the control interface, performance monitoring etc. The physics component of this task could involve the muon detection component of this trigger, in which the UW is also involved.

GLAST Simulation
Faculty: Toby Burnett

UW has a lead in the design and operation of the simulation for the GLAST satellite-based gamma ray detector, scheduled for launch in 2005. We will be designing a system to perform simulations on demand, allocating computing and data storage resources to the task. The physics involves properties of the flux of cosmic-ray particles impinging on the Earth from space, and interactions of gamma rays in matter. The latter can be studied with the simulation tool itself.

THEORY

Effective Field Theory in Nuclear Physics
Silas Beane and Effective Field Theory Group

Effective field theories (EFTs) are based on the simple idea that details of the short-distance interactions of a system of particles should not strongly affect the low-energy properties of that system. They offer ways to systematically include information on the interactions between the particles at short range while making only minimal assumptions about this dynamics. Hence, EFTs have proven extremely useful in exploring the ways in which effects not included in the "standard model" of particle physics might manifest themselves in low-energy observables.

In recent years much effort has been invested in applying these ideas in nuclear physics. We know that the forces between neutrons and protons are very complicated at short distances, and yet we believe that these complications should be irrelevant for many nuclear physics phenomena. The University of Washington has been a leader in this work. Some of us have focused on applying effective field theory to a number of aspects of the physics of the neutron-proton system. Others have been involved with the issues which arise when one attempts to apply the ideas of effective field theory to a systems of three and four neutrons and protons. This REU project is an exciting opportunity for an undergraduate student to become involved in work which represents an innovative approach to nuclear physics. It would provide training in nuclear theory, quantum mechanics and field theory which would be good preparation for graduate school courses on these topics.

Light Front Quantum Mechanics
Faculty: Jerry Miller

In 1947 Dirac introduced a new form of relativistic quantum mechanics in which the variable ct +z acts as a "time" coordinate and ct-z acts as a "space" coordinate. This so-called light front formalism was largely forgotten until the 1970's, when it turned out to be useful in analyzing a variety of high energy experiments. Despite the phenomenological success of this formalism, it has enjoyed only limited use in computing wave functions of particles and atomic nuclei. The present project is devoted to using the light front formalism to solve quantum mechanics problems involving bound and scattering states. A mathematically strong REU student would learn about relativistic quantum mechanics through the process of solving the relevant relativistic equations. This project would involve working on interesting and timely topics and could provide great preparation for graduate school quantum mechanics, field theory or even string theory.

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