:: Honors
and Awards
overview
..........................................................................................................................................................
Professor
Yodh earned his B.Sc. at the University of Bombay, and his
M.S. (1951) and Ph.D. (1955) at the University of Chicago. He has
taught
at several universities including Stanford, Carnegie-Mellon, University
of Arizona, University of Utah, and the University of Maryland, before
coming to UCI. He is a Fellow of the American Physical Society and a
Fellow
of the American Association of the Advancement of Science.
research
summary
..........................................................................................................................................................
My
current interests are concerned with the detection and study of high
energy radiation with TeV to PeV energies from astrophysical sources.
Knowing
how astrophysical sources can accelerate particles to such high
energies
provides important information about the sources themselves and
possibly
about the origin of the ubiquitous cosmic rays at these energies. Gamma
rays and neutrinos form complementary probes of the source and its
environs.
The shape of the gamma ray source spectra in the 1100 TeV region can
be
modified by attenuation of the emitted gamma radiation by intervening
galactic
or extragalactic photon fields, such as 2.7Á microwave
background
radiation or infrared radiation. Thus observed spectra provide a probe
of the nature of these fields. Neutrinos, however, suffer little or no
attenuation by these photon fields or by matter in the source and,
therefore,
provide information complementary to that of gamma rays. Studying how
these particles interact in the atmosphere will provide information
about
the particles themselves, past indications having been that the
interactions
of the particles from some of the sources are not in agreement with
expectation.
The research, therefore, investigates both particle physics and
astrophysics
and is being done using the CYGNUS and AMANDA telescopes.
Our group
has been using the CYGNUS air shower telescope to study gamma ray
emission above 20 TeV. This telescope has accumulated over 400
million
events which have been analyzed to search for emission from various
astrophysical
point sources, such as X-ray binaries, isolated pulsars, and
evaporating
Primordial black holes.
We plan to
study Very High Energy (VHE, 0.2 to 10 TeV) and Ultra High
Energy (UHE, above 10 TeV) gamma ray sources with a new Water Cherenkov
- Scintillation counter telescope (MILA-GRO) under construction. The
MILAGRO
telescope consists of a water Cherenkov detector of 5000 square meters
containing over 800 photomultipliers to detect celestial gamma rays by
detecting their electromagnetic shower. The pond exists and is located
at 8700 feet in the Jemez mountains near Los Alamos. The MILAGRO
telescope,
with its low energy threshold, enhanced angular resolution, and
continuous
operation, is well suited for elucidating the nature of particle
acceleration
and photon absorption in sources like the Crab and nearby AGNs. It will
also provide an important tool to determine whether the observed hard
spectra
from Gamma Ray Bursts (GRBs) continue into the TeV regime.
I have
taught
undergraduate and graduate courses. Topics taught have
been astrophysics, elementary particle physics, classical mechanics,
conceptual
physics, advanced laboratory and elementary laboratory.
representative publications
..........................................................................................................................................................
:: Search
for ultra-high-energy
radiation from gamma-ray bursts, D. E.
Alexandreas, et al.,
Astrophys. J. Letters, 426, L1-L3, (1994).
::
Horizontal air showers, atmospheric muons and the cosmic ray spectrum,
G. Parente, A. Shoup
and G. B. Yodh, Astroparticle Physics, 3, 17 (1995).
:: A
search for ultra-high energy gamma ray emission from five supernova
remnants, G. E. Allen, et al.,
Ap. J., 448, L25 (1995).
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