Where: Harvey Ingham Hall, Room 102
When: May 8, 2006 at 4:30 pm
"Colliding Electrons with Atoms and Molecules"
Studies of the ionization of atoms and molecules by electron impact are of interest from both fundamental and practical perspectives. They enable us to investigate the complex behavior of systems of charged particles, which underpins the electronic structure of matter, and they provide an enhanced understanding of the role played by ionization in a range of technological applications such as gas discharges, fusion physics, and laser operation. I will describe how sophisticated detector technologies and the use of spin-polarized electron beams in collision experiments enable us to highlight the mechanisms that drive electron-induced processes in atoms and molecules.
Where: Harvey Ingham Hall, Room 102
When: April 11, 2005 at 4:30 pm
"When anti-matter attacks..."
"When anti-matter attacks..." is the first line of a recent popular science article [1] highlighting research performed at UCSD. Seriously, there is no need for alarm, but recent progress in the ability to accumulate, cool, and manipulate anti-matter is leading to an increased presence of anti-matter particles in fundamental research and also in applications. I will discuss our group’s state-of-the-art scheme for positron (i.e., the anti-electron) trapping and beam formation. This technology has been exploited in low-energy atomic physics experiments at UCSD and for the formation of large numbers of anti-hydrogen atoms at CERN. I will also give an overview of new applications involving the positron in biophysics and condensed matter.
[1] E.S. Reich, New Scientist April 24, 2004
Where: Harvey Ingham Hall, Room 102
When: January 31, 2005 at 4:30 pm
"Physics in the Third Generation: Testing the Standard Model at the Energy Frontier"
Experimental Particle Physics has reached a threshold that promises new and exciting insight into the fundamental structure of matter in the coming years. Recent measurements point to new particles and phenomena that should appear at an energy scale that is almost within our reach. We are currently exploring the energy frontier with the Tevatron proton-antiproton collider at Fermilab. One important focus of the ongoing data-taking run is a detailed study of the third generation of quarks. I will discuss the current top and bottom quark measurements at the Tevatron and present preliminary results.
Where: Harvey Ingham Hall, Room 102
When: Monday, April 26, 2004 at 4:30 pm
"Black Hole Masses in Active Galactic Nuclei."
It is now widely accepted that the nuclei of most galaxies contain large black holes. The masses of these "monsters", which range between 10^6 - 10^9 solar masses, can be measured using stellar dynamical techniques, that is, by measuring the motions of stars within a few tens of parsecs of the black hole. The nuclei of about 1% of all galaxies contain luminous energy sources powered by the accretion of material onto the nuclear black hole. In these so-called active galactic nuclei (AGN), stellar dynamical techniques can not be used to determine the black hole masses. Instead, a technique known as reverberation mapping, which combines gas kinematics and the results of variability studies, has now been used to estimate black hole masses for approximately 30 AGN. Through this technique, the role of the black hole in AGN physics can potentially be studied in large numbers of AGN. But it has not yet been shown that the results of reverberation mapping are consistent with those obtained from stellar dynamical techniques. In this talk I will compare reverberation mapping and stellar dynamical measures of black hole mass using scaling relations between the black hole and the host galaxy bulge.
Where: Harvey Ingham Hall, Room 102
When: Monday, February 2, 2004 at 4:00 pm
"Magnetic molecules."
Where: Harvey Ingham Hall, Room 28
When: Monday, September 8, 2003 at 4:00 pm
"The Great Impactor."
Discovered in 1855, the star BD-1 3474 is a rather non-descript, cool red star located about 60 light years from the Earth in the constellation Serpens Cauda. However, observations conducted in the 1940s and 50s at the Leander McCormick Observatory by A. Vyssotsky, V. Osvalds and H. L. Alden indicate that BD-1 3474 is on a collision course with our Solar System. The star will pass near the Sun about 1,000,000 years from now. Assuming it passes about 2 light years away, the circumstances and consequences of the near miss will be discussed.
Where: Harvey Ingham Hall, Room 28
When: Monday, October 28, 2002 at 4:10 pm
"In Search of Things that Shouldn't Be -- and Patterns in Things that Are."
Kaons themselves were first found as "something that shouldn't be", and their interactions have a rich history of surprises. I will introduce kaons and talk about some of my present and past work exploring some of those surprises. One question is: when do we know? or how to assess the uncertainties in our knowledge and measurements? You have probably worried about that same question in your own physics measurements. I will give you some case studies also. One result I have been working on for the past decade (a long time for an experiment!) is a search for the forbidden decay K+ -> pion muon electron. Why it is forbidden, how we have searched for it, and its present status will form a large part of the talk.
Refreshments and cookies served at 4:00 pm before the seminar.