In the past two years since my advancement to PhD candidacy, I have studied the methods of medium and high energy particle physics. My dissertation topic focuses on the observation of relativistic antihydrogen atoms produced in Fermilab experiment E862.
Experiment E862 detects antihydrogen created when an antiproton from the 3-9 GeV/c momentum beam at the Fermilab Antiproton Source is intersected by a cryogenic, molecular gas target which emits hydrogen clusters in the form of a jet. An electron-positron pair can be formed when the antiproton travels near a target nucleus. If the relative velocity is small, the positron can form a bound state with the antiproton. The electrically neutral antihydrogen will continue virtually straight on a tangential path out of the ring which contains the antiproton beam and bends any other charged particles. Eighty feet in a straight line downstream of the jet, a thin foil target ionizes the antihydrogen atom. The positron is bent out of the way with small spectrometer magnets and is detected with a scintillator. It annihilates and the gamma rays are detected by a sodium iodide detector. The antiproton is detected in an 80 foot beamline with wire chambers and bend magnets to measure the momentum. The Cern experiment PS210 detected the very first antihydrogen atoms using essentially the same method in 1995. Production of antihydrogen by other means has been so far unsuccessful.
After receiving the masters degree from UCI in physics, I spent about 2 years performing an analysis on two body meson final states from the Fermilab E760 data taken in 1991. This included reconstructing and filtering neutral trigger data from the experiment, calculating Monte Carlo generated geometrical acceptances final cross sections. This culminated in a Physical Review publication.
Also for the past two years, I have been involved with the initial design of the antihydrogen experiment and started assembling the data acquisition electronics, refurbished the wire chambers, performed rate tests and was involved in assembling and testing our three element magnetic spectrometer for detecting positrons. A two week stay at the US Particle Accelerator School in 1993 helped me to understand some of the fine points of working with beam manipulations. Final assembly and cabling in the experiment tunnel followed by extensive calibration ended in October 1996, when we saw our first antihydrogen candidate. Since then, procedures for running the experiment were developed so that the experiment could be run remotely. Since I have been the only graduate student on the experiment whose members number only seven, I have gotten a chance to learn all the nuts and bolts needed to design, build, and analyze a complete, high energy physics experiment.
So far, 63 clear candidates have been observed with no background. Most have a ~6 GeV/c momentum. Reconstructing events, and understanding the data as well as removal of systematic effects has now become of paramount importance as we wish to measure the antihydrogen production cross section to 10% as well as to assess the energy dependence of the cross section.
The significance of the antihydrogen system in the long run is the ability to compare to its matter counterpart, hydrogen, whose energy levels are known exactly. Small matter-antimatter differences would point to violations of fundamental theory such as a CPT symmetry violation. An upgrade of E862 will attempt to measure the spectroscopy of the antihydrogen n=2 energy levels by using an interference method. Designing apparatus which will measure the fine structure and Lamb shift in the next Fermilab running cycle is currently ongoing.
Other collaborators on the experiment are Mark Mandelkern, Keith Gollwitzer, George Zioulas and Jonas Schultz, all at UCI, David Christian at Fermilab, and Charles Munger.