In the analysis of top quark events at the Fermilab Tevatron, the largest theoretical uncertainty is due to the Quantum ChromoDynamic (QCD) corrections in the top quark production and decay. In this project the REU student, along with the advisor, will investigate the perturbative calculation of these corrections with the goal to make them more amenable to phenomenological analyses, with motivation from parton shower Monte Carlo simulations. This will be done by considering the process of top quark decay to a bottom quark and a W boson, with or without an additional emitted gluon. Basic techniques and issues in QCD and weak interaction physics will be learned by the student along the way. This project will involve some computer programming. (The advisor generally programs in C++.)
We invite a student to participate in research on the structure of nuclei far from stability and the development of a new array of Germanium detectors at the National Superconducting Cyclotron Laboratory. Knowledge of LabVIEW and C++ are requested.
An Amphiphilic molecule consists of two parts with opposite characters: a water loving (hydrophilic) ``head'' and a water avoiding (hydrophobic) ``tail''. Because of this duality in one unit, they can arrange themselves in a variety of structures in water, ranging from globular and cylindrical clusters (called spherical and cylindrical micelles), to bilayers, or vesicular structures. Surfactants, which occur in soap that we use everyday, phospolipid molecules, that occur in biological systems are examples of such amphiphiles. Studies of amphiphiles and other soft condensed matter systems, such as, polymers, membranes etc., have become an important area of research in recent years. Not only they show promises for prospective technological applications, but the physical phenomena occurring in these systems are often very different than that of small molecular systems.
The project will involve to understand physics of these complex fluids in terms of simple lattice models using Monte Carlo simulation. The student will learn how to compute thermodynamic quantities such as average energy and entropy associated with these micelles. The project will also involve the study various shape transformations that occur in these systems by monitoring appropriate quantities, e.g., moment of inertia, cluster distribution function etc. The simulation results will be compared with the existing theoretical predictions and experiments.
The HEP group has a number of projects relating to two experiments at the energy frontier: CDF at the Fermilab Tevatron Collider (near Chicago) and ATLAS at the LHC (Large Hadron Collider). The Fermilab Tevatron Collider looks at proton-antiproton collisions at a center-of-mass energy of 2 TeV and is currently undergoing an upgrade and is scheduled to start running again in the spring of 2000. At the LHC, a two proton beams collide at a total center-of-mass energy of 14 TeV. The LHC is scheduled to start running in 2005. Most of the projects involve the construction and testing of detector components to be used in these two experiments, along with the possibility of the analysis of data that has already been taken with the CDF detector.
When a charge localizes in a lattice made up of charged ions, such as a metal-oxide, it induces a structural distortion. The resulting ``quasiparticle'' consisting of the localized charge and the structural distortion is called a polaron. It can hop about and carries charge so is a charge carrier like a very heavy electron. Using recently developed scattering techniques we have measured directly for the first time what these polarons look like. The materials we have been studying have the formula LaMnO3 and they have exotic electrical properties. This summer's project is to use 3-dimensional rendering software to make a visualization of the charge localization, polaron forming, process. Ultimately we would like to make a video showing the polaron forming process and then the polaron dynamics. If possible we would also like to make a virtual reality video of what it looks like to be sitting on a manganese atom when a charge localizes on you. We will use a commercial product called Cerius2 which runs on a Silicon Graphics computer. The software and computer are being purchased right now and will be here in time for the program. The project will involve learning how to program the software, understanding the basic physical concepts, and then ultimately making the visualizations. These will be used in presentations and posted on the web. There are no special skills required for this project but a well developed imagination and prior experience with computers are desirable qualities.
It has been suggested [T. Egami, private communication] that the taste of chocolate is, in part, determined by its atomic structure. For example, a chocolate bar which sits on a windowsill, partially melts, then resolidifies, turns from a delicious smooth soft object to a hardened, bad tasting, worthless lump. What changed? The suggestion is that the local structure rearranged on an atomic level. We would like to investigate this using a novel scattering technique, the atomic pair distribution function (PDF) technique which we have been pioneering in our laboratory. It is also an interesting possibility that these ideas can be extended beyond chocolate to other foods. This is a novel extension of an ongoing research goal in the group of relating local atomic structure to properties....in this case the property is taste rather than electrical or magnetic properties which are the properties we have focussed on to date.
The project will involve sample preparation, collecting and analyzing x-ray diffraction data in our laboratory, and disposing of the samples after the experiment. The student will work with post-docs in the lab to learn how to use the equipment and will participate in other (more conventional) experiments as part of a group, as well as the study of the structure-taste relationship. Some knowledge of x-ray diffraction, crystal structure and basic computer use is helpful but not required. This work will involve hands-on experiments and computer based data analysis.There are numerous aspects of using computers in the teaching/learning environment. Their use has the potential for enhancing both effectivness and efficiency, as they may be able to provide to a very large group of students the type of instruction and learning interactions usually reserved for small classes. In the study of physics, it has become increasingly evident that the conceptual aspects of the field are the major hurdle for most students. They often reach for a formula, then plug and chug, hoping that the answer is correct. The correlation between the understanding of concepts and overall performance is extremely strong. The design of questions and exercises dealing with concepts is a highly beneficial process for instructors, as part of the process is to identify misconceptions and designing methods that will induce students to shed these misconceptions.
In this REU project, the student will participate in all aspects of preparation of such exercises, from the identification of the misconception to the final coded work ready for use in a class. The tool used is CAPA, a networked tool developed to implement a Computer-Assisted Personalized Approach for assigments, quizzes and examinations. The particular topics involved in the project will be determined after discussion with the REU participant. A second aspect of the project is the analysis of the feedback received by students to help improve the effectiness of the system.
From basics of quantum mechanics you know that a quantum particle can penetrate a potential barrier, an achievement impossible in the world governed by classical mechanics. Strangely enough, only very little is known on how a composite object of finite size can tunnel although one frequently encounters problems of this type in nuclear, molecular or condensed matter physics. Depending on the character of the binding, the constituents can tunnel sequentially or simultaneously; their interaction can hinder or facilitate tunneling. Especially interesting situations emerge if the barrier acts only on a part of particles (for example, the Coulomb barrier exists only for charged particles). Our goal is to try to understand the rules and regularities of these phenomena.
We can analyze the static flexibility of a protein using a new algorithm developed at MSU. In this project we will seek to examine the dynamic motion of small flexible pieces of protein that are functionally significant. This will be done by building some plastic models and using Monte Carlo simulations. No prior knowlege of proteins or biochemistry is required - although some programming familiarity would be useful.
As an example we will use the HIV protease protein which is part of the HIV virus and study the action of the main-flaps whose motion is inhibited by a number of very successful anti-aids drugs that have recently come on the market. If you have some interest in biophysics and/or biochemistry this would be a good way to see what kind of research a physicist can do in these areas and how it is relevant.
We have recently discovered that some of the search and network optimization algorithms used in computer science solve some ``hard'' problems in physics. Two REU students may join my group of 3 grad. students working in this area and learn some computer science, some physics problems related to self-organized criticality and fractals, and how to analyse data using scaling and self-similarity. Interest in and aptitude with computers is necessary.
RR Lyrae stars and Cepheids change in brightness because they pulsate, periodically increasing and decreasing in both radius and surface temperature. Such stars have two important roles in modern astrophysics: (1) they serve as test objects for theories of stellar pulsation and evolution and (2) they serve as standard candles for determining distances beyond the immediate solar neighborhood. In this project, we will discover the properties of variable stars in two areas, the Small Magellanic Cloud and the solar neighborhood. For the Small Magellanic Cloud, one of the satellite systems of the Milky Way, we will be completing an analysis of data already obtained with a CCD detector on the schmidt telescope at Cerro Tololo Observatory in Chile. The solar neighborhood part of this project will involve taking photometric data of RR Lyrae stars with the 24-inch telescope on campus.
We study the electronic structure of charge density wave and thermoelectric materials using angle resolved photoelectron spectroscopy. Prospective REU student(s) will be involved in data analysis and photoemission instrumentation on campus. We may also travel (for one to two weeks) to the Synchrotron Radiation Center, a national research facility operated by the University of Wisconsin-Madison, to conduct experiments.
Dichotic pitch is a binaural effect wherein the phase relationships between left and right ear signals create a sensation of pitch even though both signals are spectrally white. This summer's project is primarily an experimental attempt to relate dichotic pitch to lateral inhibition among the neurons of the superior olivary complex of the midbrain, as exhibited in temporal masking experiments. Rather good ears are very useful in this project.
Binaural cross-correlation: The superior olive complex of the midbrain processes interaural differences in narrow frequency bands. Therefore, it becomes possible to represent the binaural cross-correlation function by perturbations on standard forms for each frequency band. This project is mostly a theoretical study in linear physical acoustics. Reasonable computational skills are needed.
The sound that comes directly from a source to a listener provides valid localization information of many types. Sound that is reflected from the surfaces of the environment is thought to provide only interference. The localization project discovers how listeners perceptually cope with this interference under a wide variety of signal and room conditions. The project is mostly experimental and requires dealing sensibly with a lot of data.
The giant dipole resonance (GDR) is a collective vibration observable in all nuclei. It can be explained as a vibration of all the protons versus all the neutrons. It persists also in hot nuclei which can be produced by populating highly excited states with nuclear reactions. The GDR can then be studied via its gamma-ray decay.
We have recently measured the width of the GDR as a function of the excitation energy (temperature) in Pb and Sn nuclei. The experimental data are published in Physical Review Letters, and many theoretical groups around the world perform calculations in order to explain the data. The resonance widens as a function of temperature either because of the coupling to larger and larger collective shape variations of the nucleus or because of increasing collisions between individual nucleons inside the nucleus. The final comparison between the theory and the data requires a close collaboration which we established with several of the theorists. The REU project involves the incoporation of the models into a statistical decay model code used to describe the data. The results of the comparison of the calculations with the data will be very important and will most likely lead to a scientific publication.
Using a new Hartree-Fock hamiltonian which I have recently developed, the student would calculate the binding energies for all nuclei and compare with experiment. Some phenomenological interactions will need to be developed to describe the rotational correlation energy. The location of the neutron and proton drip lines is a related topics of particular interest.
In the first few microseconds after the Big Bang, the universe existed as a quark gluon plasma. The quarks that we now see confined inside neutrons and protons were free to move around. We are planning to recreate these conditions at the Relativistic Heavy Ion Collider (RHIC) and study the collisions of gold nuclei using the STAR detector. RHIC and STAR are located at Brookhaven National Laboratory on Long Island, New York. This summer we will carry out simulations of the phenomena that we want to study at STAR including disoriented chiral condensates, charge correlations, and flow. In addition, we will participate in the construction of the electromagnetic calorimeter for STAR by assembling the optical fiber systems.
See http://www.rhic.bnl.gov, http://www.star.bnl.gov, http://westfall.tcimet.net
Solid state Nuclear Magnetic Resonance (NMR) is a novel approach to macromolecular structure determination and involves measurement of specific interatomic distances and angles with radiofrequency pulse sequences and magnetic fields. We are currently using solid state NMR to investigate the structures and dynamics of both AIDS-related proteins and magnetic materials. The AIDS proteins bind to human receptors and antibodies and structural data for them should greatly aid in the development of HIV vaccines and therapeutics. In addition to our disease and materials-specific research, we also develop new solid state NMR techniques for biological and other macromolecules. Our work includes NMR physics, analytical quantum mechanical calculation and computer simulation, building apparatus, and RF electronics. For more information, please e-mail me at weliky@cem.msu.edu.
The development of radioactive ion beams at the National Superconducting Cyclotron Laboratory (NSCL) has allowed access to new regions of the chart of the nuclides for the elucidation of the decay properties of exotic nuclear species. In an experiment carried out at the NSCL (May 1999), a primary beam was fragmented by a Be target to produce a series of neutron-rich nuclides. An REU student will participant in the analysis and interpretation of results from this experiment. This will include the use of the NSCL data analysis programs to examine beta-gamma and gamma-gamma coincidence data from ground state decays. The particle-triaxial rotor model (PTRM) will also be applied to understand better the systematic trends in the low-energy structure of these nuclides.
The National Superconducting Cyclotron Laboratory is capable of producing radioactive beams by passing a stable beam through a thin target. The secondary beams which may consist of exotic nuclei can then be refocused for further study. Using the S800 spectrograph, we study reactions involving secondary beams where the exotic nuclei react with a second target. By measuring the particles which are knocked out of an exotic nucleus in the second reaction, one can probe the structure of the exotic nucleus. The REU student would participate in the running and/or analysis of such experiments.
Using secondary radioactive beams of exotic nuclei, the Miniball collaboration at the NSCL will investigate reactions involving the exotic nuclei with targets, where protons or neutrons are exchanged between the target nucleus to the exotic nucleus. These reactions are sensitive to the nuclear quantum wave functions of the outermost protons and neutrons. The REU student will be involved with both the running and analysis of an experiment planned for this summer.
Nucleus-nucleus collisions at the NSCL are used to probe nuclear matter. In mid central collision, more fragments originate from the neck of the colliding system than evaporation from either the projectile-like or target-like spectators. Thus neck fragmentation provides a promising new observable with which to test dynamical fragmentation models. In this project we'll examine the isospin dependence of the neck fragmentation between the proton-rich 112Sn+112Sn and the neutron rich 124Sn+124Sn systems.
In a survey with broad-band colors, we have discovered a class of objects with power-law spectra, which are unlike that of stars and galaxies. In one sample in the south galactic hemisphere, they were found to be near galaxies at redshift z<0.3. The REU project is to search for them in an independent sample, to look for morphological peculiarites, and to test for other spatial correlations. These will offer clues to the nature of these objects.
We are studying spin-polarized transport of electrons in metals, at a mesoscopic length scale. What does that mean? When electrical current flows from a ferromagnet into a normal metal, the current consists of an unequal number of electrons with up and down spins; i.e. the current is partially spin-polarized. You might guess that the spin-polarization doesn't last forever; rather, it dies away because electrons occasionally flip their spins in the normal metal. Nevertheless, the spin polarization lasts long enough to be useful for a wide variety of spin-dependent electronic devices, such as the read head in your hard disk drive. We are measuring the decay of the spin polarization directly, using local probes of the spin polarization along the wire. The probes are spaced apart by a distance less than one micron, hence the term "mesoscopic" -- smaller than you can see, but large compared to atomic sizes. An REU student could help us in this project by testing the tunnel junctions used to measure the local spin polarization. The project will involve learning microfabrication techniques as well as how to make electrical measurements of very small structures.
Planetary Nebulae are expanding shells of predominantly hydrogen gas containing about .1 x the mass of the sun and moving radially at about 10 km/s. They result from the expulsion of the envelope of a red-giant star with a radius of about 100 x the radius of the sun during the late stages of the life a star. The vast majority of stars including the sun will suffer this fate with the core of the star containg most of the mass of the red-giant star becoming a white dwarf star. The structure and dynamics of the expelled envelope (the planetary nebula) are determined not only by the expulsion process, but more importantly by the heating of photoionizing radiation (photon energy >13.6ev) and ram pressure of a high speed wind (wind speed > 1000km/s). Dense condensations can form in the planetary nebulae harboring molecules and dust particles at temperatures of 100k or even 10k in an environment where the bulk of the gas in the planetary nebula is maintained at about 10000k through the balance struck between heating through photoionization of hydrogen and cooling by collisional excitation of trace elements such as oxygen which radiate at characteristic wavelengths. Complete theoretical calulations of the overall structural and dynamical evolution of planetary nebulae are being conducted including analysis of the effect on the structure of the interstellar medium into which the planetary nebulae are injected. Help is needed with the computer generated graphical representation of the time-dependent distribution of density,temperature,velocity and state of matter (plasma, neutral atomic, neutral molecular, particulate).