The following text was automatically extracted from the image on this page using optical character recognition software:
237
Model through a test of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM)
matrix. Neutron beta decay also provides the time scale for Big Bang
nucleosynthesis and remains the largest uncertainty in cosmological models that
predict the 4He abundance.
Category three involves the study of the weak interaction between quarks in the
strangeness-conserving sector. This study is very difficult because of overwhelming
direct effects of the strong interaction. As a result, the effective weak couplings in
the usual meson-exchange model of the process are poorly known. In fact, different
experiments yield contradictory results. Sensitive experiments using polarized cold
neutrons to determine parity violation (an unambiguous tag for the weak
interaction) in the n-p, n-D, and n-4He systems provide an opportunity to measure
NN weak interactions in simple systems that are not complicated by unknown
nuclear structure effects. Knowledge of these interactions is required to understand
parity violating phenomena in nuclei, such as the recently discovered nuclear
anapole moment, and can be used to gain information on quantum chromodynamics
(QCD) in the strongly interacting limit.
Category four examines stellar astrophysics and the origin of the heavy
elements. Light element nucleosynthesis occurred during the first few minutes of
the big bang; however, all isotopes with an atomic mass number greater than seven
are created only in stellar processes. Typically, these stellar processes ("r, s, p, etc.")
involve competition between neutron capture, which moves isotopes to increasing
atomic mass number and beta decay, which increases atomic number. The relative
abundances are particularly sensitive to the neutron capture cross sections of
radioactive nuclei with lifetimes comparable to s-process time scales (months to
years). Intense neutron sources in the few keV energy regime (corresponding to
stellar temperatures) provide the only experimental method of obtaining this
information.
Neutron interferometry (category five), perhaps the most ideal realization of
Schrodinger wave optics, has been employed to elucidate a number of phenomena
in non-relativistic quantum mechanics. In addition, neutron interferometry is
currently being used to perform precise scattering length measurements, which will
eventually improve our knowledge of the electromagnetic structure of the neutron
and address the question of nuclear three-body forces. Many important experiments
have been suggested, but as the technique is extremely count-rate limited, only a
subset of these have been performed. An intense pulsed source offers the possibility
of extending these efforts into the study of time-dependent phenomena, opening up
a range of new investigations.
Activities in fundamental nuclear physics are focused at a few high-flux
facilities in Europe and the United States. The premier facility is the Institut Laue
Langevin (ILL) in France, whose reactor is the highest flux continuous neutron
source in the world. The ILL has maintained a vigorous program of fundamental
neutron physics since the early 1970s and has, in the past, been quite open to
foreign scientists. Researchers from the United States have been heavily involved in
