Professor
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.
Revised January 19, 2000