Session BA: Neutrinos and Fundamental Symmetries

Weighing Neutrinos

Neutrino oscillation experiments performed throughout the latter half of the twentieth century have yielded valuable information on the nature of neutrino masses and mixings. The evidence gathered has provided the first positive evidence for physics beyond the standard model. As the next century begins, a new suite of precision experiments will come online to provide greater insight into the physics and significance of neutrino mass. This talk will review our current state of knowledge on neutrino masses, and how new experiments will complement that knowledge in years to come.   

Electric Dipole Moment Searches for T-Violation

An active program of new searches for T-violating Electric Dipole Moments (EDM) is underway. This effort has been stimulated by recent work on both the theoretical and experimental fronts. In theory, detailed studies of physics beyond the standard electroweak model suggest that new T- and CP-violating phases naturally appear. In experiment, new techniques are being applied to well-studied systems to greatly improve the sensitivity and, in addition, new systems are being identified that also suggest significant improvements in sensitivity may be possible. The recent results and plans for future EDM experiments will be discussed, including studies of the neutron, deuteron, atoms and molecules.   

UCN for Testing Fundamental Symmetries

For the field of neutron physics, standard model of particle physics requires two parameters, the quark mixing CKM matrix element V$_{ud}$ and the ratio of axial vector to vector coupling constant $\lambda$ for nuclear $\beta$ decay, which are obtained from neutron life time and beta decay correlation measurements. Nuclear astrophysics requires the neutron life time to explain nucleosynthesis in the early Universe after the Big-Bang. Theories beyond the standard model, which may explain the baryon asymmetry in the universe, require neutron EDM measurement. Ultracold neutrons (UCN), which are very low energy neutrons, have a unique role in these measurements, because UCN are confined in a material bottle and a magnetic bottle, where the neutron life time, the neutron EDM and also the $\beta$ decay correlation are measured. In the experimental bottle, UCN are distributed to a phase space, where the volume of the bottle as well as the maximum UCN energy is limited. Therefore, UCN phase space density is very important for these measurements. A number of groups are developing new generation UCN sources in the world. The new generation UCN sources use phonon phase space for cold neutron cooling so that the UCN phase space density is not limited by Liouville's theorem, and then increases above the value of the Maxwell-Boltzmann distribution for the cold neutrons. Experiments with the new generation UCN sources will greatly develop the field of fundamental neutron physics.