September 1
NO COLLOQIUM - FACULTY MEETING
September 8
Craig Ogilvie, MIT Department of Physics
10^12 Degrees in the Shade
Host: Betts
Abstract: Most of normal, everyday matter is made up of hadrons, e.g.
the neutrons and protons inside a nucleus. Inside every hadron are the
more fundamental particles, quarks and gluons. An outstanding scientific
puzzle is why quarks and gluons are never found outside a hadron but are
confined to exist within this small volume. New experimental information
on this question might be at hand. If you can heat or compress nuclear
matter such that the protons and neutrons significantly overlap, then the
quarks and gluons will no longer be confined to a single hadron and can
travel larger distances. This not-yet-discovered state of matter is known
as a quark-gluon plasma. The temperature necessary to make a plasma is
estimated to be near 10^12 K, conditions that existed some micro-seconds
after the Big Bang. Hence one goal of our work is to create and study a
small volume of the early universe in the laboratory.
To do this we accelerate then collide two large nuclei at very high energies. If sufficient energy is deposited during the collision, the system may be hot and dense enough to form a plasma. Such a plasma can only be short-lived. The heated matter expands, cools, and the quarks are "re-confined" into several thousand hadrons that stream towards our detectors. The experimental challenge is to find compelling evidence from this hadronic debris for the fleeting existence of a quark-gluon plasma. The search for the plasma will be reviewed in this talk, with emphasis on the strangeness signature, as well as the prospects at a new accelerator (RHIC) that started commissioning this summer.
September 15
Heinz Pernegger, MIT Department of Physics
The state-of-the-art in Particle Detection:
Silicon detectors in High Energy and Heavy Ion Physics
Host: Betts
Silicon detectors are the forefront instrumentation in heavy ion and
high energy physics experiments. Their unique properties of being very
compact detectors with extremely high granularity makes them the ideal
choice for particle detection near the interaction region of collider experiments.
Two examples of state-of-the-art silicon detectors will be present to illustrate
the broad range of physics that can be accessed with silicon detectors.
The DELPHI Silicon Tracker tracks the decay products of B-mesons
in the search of the Higgs boson at LEP2. The silicon detectors of the
PHOBOS experiment will measure particle multiplicity and spectra produced
in Au-Au collisions at RHIC in the quest for the Quark-Gluon-Plasma. I
will show how the same detector technology can achieve spatial resolution
in the micrometer range or be used for measuring thousands of particles
at the same time. The presentation will conclude with most recent developments
in this field, like detectors based on CVD diamonds, and their prospects
for future experiments.
September 22
Chris Quigg,
Theoretical
Physics Department,
Fermi National Accelerator
Laboratory
Coming Attractions in Particle Physics
Host: Varelas
Abstract: Particle physics has developed with remarkable swiftness
over the past twenty-five years, with the establishment of quarks and leptons
as the constituents of matter and a deepened understanding of the role
of symmetries in shaping the physical world. The conceptual framework in
which we have learned analyze the universe, the ``standard model'' of particle
physics, is a tool for exploration and discovery. I will explore some of
today's urgent questions and the means by which we hope to answer them,
then look over the horizon to the questions we are just learning to formulate.
I will conclude by showing how recent insights inform our understanding
of the everyday world.
September 29
Farid F. Abraham, IBM Research Division, Almaden Research
Center, San Jose CA 95120
Cracking a Tough NUT* With a Big Computer
Host: Batra
Abstract: With the advent of parallel supercomputers, atomic simulations
are > providing immediate insights into the nature of materials failure
by allowing us to "see" what is happening on the atomic scale. We discuss
the simple concepts of "how things break." These concepts will be
illustrated by different "computer experiments" showing brittle fracture
(breaking glass), plastic deformation (denting a fender), and supersonic
crack propagation (earthquake fault slippage). Two videos will be
shown. Multimedia versions of our atomic simulation studies of fracture
is available at http://www.almaden.ibm.com/st/Simulate/Fracture
*Nanocrystal Under Tension
October 6
Andreas Schroeder, UIC Department of Physics
How to Build a Kilovolt X-Ray Laser
Abstract: The direct in vivo visualization of protein function and
cellular molecular structure with atomic-scale resolution has long been
a goal of the scientific community: today the need is for rapid determination
of complete genome protein structures, and tomorrow the need will be for
resolution of the dynamics of these structures and their assemblies as
nano-biomachines. Although interferometric techniques (e.g. Fourier transform
holography) for such a visualization are well understood, a suitable radiation
source for this type of measurement has not been developed, mainly because
of the stringent requirements placed on it. Specifically, the radiation
source must be spatially and temporally coherent, have a wavelength of
~1Angstrom, be of sub-picosecond duration, and possess a brightness in
excess of 10^30 photons/(sec mrad^2 mm^2)/(0.1% bandwidth). I will
discuss the reasons for these requirements and detail the means by
which they could be met in laser-pumped atomic cluster targets. In
particular, I will present a theoretical analysis of and experimental evidence
for a quantum-state selective, laser-driven, collisional ionization mechanism
which is capable of generating population inversion in the inner shells
of high Z atoms; that is, precisely what is required for a coherent
kilovolt x-ray source (or x-ray laser).
October 13
NO COLLOQUIUM - FACULTY MEETING
October 20
David Grier, University of Chicago, James Franck Institute
Like-Charge Attractions and Related Macroionic Mysteries
Host: Marko
Abstract:
Small charged particles dispersed in a fluid are supposed to
repel each other. These repulsions are widely believed to endow
colloidal and polyelectrolyte suspensions with their interesting
and useful properties. New experimental techniques make possible
the first direct measurements of the tiny forces which characterize
colloidal interactions and reveal that, quite often, mesoscopic
particles carrying the same sign charge actually attract each other.
These anomalous long-range attractive interactions are not explained
by established theories for electrolyte interactions and are likely
to affect the properties of many natural and industrial suspensions.
October 27
Edward Bulcher, University of Chicago
Investigating the Difference between Matter and Antimatter
with Neutral Kaons
Host: Varelas
The origin of CP violation, which is thought to be necessary for
understanding the striking asymmetry in the abundance of matter and
antimatter in the Universe, is one of the fundamental questions of
particle physics. In 1964, Christenson, Cronin, Fitch, and Turlay
found evidence for the violation of CP invariance in the neutral K system.
The effect they discovered could be explained by a small imbalance between
K0 -> K0 bar and K0 bar -> K0 mixing. Since their discovery, physicists
have searched for "direct" CP violation, in which the CP symmetry is
violated in the decay process. During the last year, experiments at
Fermilab and at CERN have definitively established the existence of this
new form of CP violation.
November 3
James Sauls,
Department
of Physics and Astronomy, Northwestern University
Discovery of the Acoustic Faraday Effect in Superfluid
3He
In 1957 Landau predicted that the quantum liquid phase of 3He
would exhibit transverse sound, ie. propagating shear waves, at
low temperatures. These waves have recently been observed at ultra-low
temperatures in the superfluid phase of liquid 3He.1
The new observations provide a beautiful example of spontaneous symmetry
breaking in liquid 3He. I will describe the physics of tranverse
wave propagation in quantum liquids and the recent detection of these waves
by magneto-acoustic rotation of the polarization in a magnetic field, the
acoustic analogue of the magneto-optical effect discovered by Michael Faraday
in 1845.
1. Y. Lee, et al.,
Nature
400, 431 (1999).
Host: Marko
November 10
Fernando A. Ponce, Arizona State University, Department
of Physics and Astronomy, Tempe, Arizona 85287-1504
The Nitride-Based Revolution in Light-Emitting Devices
Host: Sivananthan
***Prof. Ponce will also give a Condensed Matter Seminar
on Nov. 11***
Abstract: Recent advances in fabrication technologies for the semiconducting
nitrides in the group III elements* have led to commercially available,
high efficiency solid-state devices that emit green and blue light.
The performance of these GaN-based blue and green light emitting devices,
as well as recently-developed high efficiency AlGaInP-based red devices,
have surpassed the performance of incandescent lamps, and are currently
challenging the fluorescent sources. Light-emitting diodes based
on these materials should find applications first in traffic lights and
flat-panel displays. Blue and ultraviolet laser diodes promise high-density
optical data storage and high-resolution printing.
These exciting technological advances are due to
the unique microstructures associated with growth of GaN/InGaN heterostructures
under unusual conditions. Large defect densities (~1010 dislocations/cm2)
play a key role in the relaxation of thermal stresses, and allow the growth
of high quality films. The nature of the substrate/thin film interfaces
will be discussed, as well as the role of the buffer layer. Details of
the microstructure and correlation with light emitting properties will
be presented. Recent developments including the commercialization
of continuous operation blue laser diodes will be discussed.
(*) F. A. Ponce and D. P. Bour, Nature Vol. 386, 351 (1997).
November 17
Adrianos Melissinos
Breakdown of the Vacuum by an Intense Electromagnetic
Field
Host: Varelas
Abstract: We have observed the production of e+e- pairs when a high
energy (46.6 GeV) electron traverses the focal area of an intense
(terawatt) laser pulse. From kinematic considerations alone this
process involves the absorption of at least five laser photons (of
energy 2.34 eV). Alternately one can interpret the results as spontaneous
breakdown of the vacuum induced by the electromagnetic field of the
laser pulse. Indeed, in the rest-frame of the incident electron the
electric field approaches the Schwinger critical value E=1.3x10^16 V/cm.
November 24
Misha Stephanhov, Russell Betts and Tom Imbo
Research Opportunities In Particle Physics
for Graduate Students
(3 short talks by UIC physics faculty)
December 1 - NO COLLOQUIUM - FACULTY MEETING
December 8 - NO COLLOQUIUM - FINALS WEEK
If you are driving, you can park in any of the public parking lots. Parking Lot 4 at the northwest corner of Halsted and Taylor is most convenient, although occasionally full. Speakers should ask their hosts for a parking validation sticker.
If you are arriving at O'Hare International Airport, you can travel to UIC directly by subway (CTA Blue Line). This costs $1.50, and takes you from inside the airport to the UIC-Halsted CTA Station (at Halsted and Harrison), a few blocks north of the department, in about 50 minutes. Alternatives include taxi (roughly $30 to downtown Chicago), or the Airport Express limosine, which can take you to the Quality Inn at Madison and Halsted (1/2 mile north of campus) for about $15.
If you are arriving at Midway Airport which is southwest of UIC, subway travel is possible (Orange Line to downtown, then change to the Blue Line), but it is much faster to take a taxi ($20).
Map
of UIC East Campus North of Taylor Street (shows Parking Lot 4 and UIC-Halsted
CTA Station)
Map
of UIC East Campus South of Taylor Street (shows SES Building and alternate
public parking)
MapQuestWeb
Map of UIC Area
