Rutgers University Department of Physics and Astronomy
High energy experiment
Astro-Particle Physics: the HiRes Experiment.
I am involved in the High Resolution Fly's Eye Experiment (HiRes). This experiment is studying the highest energy cosmic rays: particles of order 10**17 - 10**20 eV that strike the earth's atmosphere. They initiate giant showers in the atmosphere and our experiment detects these showers by the fluorescence light emitted by nitrogen atoms excited by the shower particles. The detectors are located on the tops of two desert mountains in west central Utah where the "seeing" is very good.
The interactions of cosmic ray protons of energy greater than about 6 x 10**19 eV with the cosmic microwave background radiation is an important energy-loss mechanism for these protons, and is expected to be so strong that no particles above this energy should be seen if their sources are farther away than about 50 Mpc. The nearest known source that is large and energetic enough to accelerate a proton to such an energy is about 100 Mpc away, so our expectation is that no cosmic ray protons above this energy should exist. This is called the GZK limit. In 1991 a previous generation of our experiment observed a cosmic ray particle of energy 3.2 x 10**20 eV, and a handful of additional particles above the GZK limit have been observed by other experiments since that time. This is a serious dilemma.
The goal of our experiment is to first confirm with good statistics whether the GZK limit is actually violated (our preliminary data indicate that it is), and second to study these remarkable events. For example we will measure their arrival directions. If they all came from the same point in the sky one would expect that the dilemma would have an astrophysical solution: some new type of astrophysical source would be located there. If they were isotropically distributed then perhaps a particle physics solution to the dilemma would be indicated: perhaps there exists a metastable particle of enormous mass, created at the time of the big bang, and we are seeing its decay products. Either case is very interesting.
Our group consists of a postdoc, graduate and undergraduate students, and myself. We are building apparatus, taking data in Utah, and analyzing these data to study the high energy cosmic rays.
Particle Physics: the KTeV Experiment.
With Stephen Schnetzer and Sunil Somalwar, I am participating in the KTeV experiment at Fermilab. This experiment involves research on the source of the violation of Charge-Parity (CP) symmetry using a beam of neutral K mesons. CP violation is one of the least understood aspects of the current Standard Model of particle physics. It is believed to be related to the matter-antimatter asymmetry that became manifested in the early universe. Determining whether the magnitude of CP violating amplitudes are consistent with the Standard Model is currently one of the most important issues confronting particle physics. Since the KTeV experiment provides an extremely intense beam of neutral K mesons, it also provides a rich source of thesis topics involving the measurement of various rare decay modes of the K mesons. The KTeV experiment is a relatively small High Energy Physics experiment, and our students have the opportunity to master all aspects of research, such as hardware, software, and particle physics which is the driving force behind the experiment.
Superconducting RF Cavity R&D.
I am collaborating in a project centered at Fermilab to develop superconducting RF cavities to build a novel beam that consists of K+ mesons, called an RF-separated kaon beam. This work is being done in collaboration with Helen Edwards' group at Fermilab.
Please send any comments on this page to Gordon Thomson, Thomson@ruthep.rutgers.edu.
Revised January 19, 2000