31 research outputs found
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Measurements of parity violation in neutron-nucleus reactions
In this talk I describe a new generation of experiments studying the weak interaction between nucleons. Measurements of the effect of this interaction are few in number and the significance of the observed effects are generally small. It is well known that the weak interaction violates parity. This was first experimentally established by C. S. Wu through measurement of an asymmetry of electrons emitted in the beta-decay of polarized {sup 60}Co. The measured asymmetry was large because beta decay is a weak interaction process. For a process in which the strong interaction can contribute, we expect much smaller asymmetries, of order 10{sup {minus}7}. In the work I will describe here we study the effects of the weak interaction through the signal of the parity violation associated with that interaction. There are two basic classes of experiment used to detect parity violation. The first relies on the measurement of a cross section or width that would vanish if parity were conserved. One example of this type of experiment in nuclear physics is the decay of an unnatural parity state to a 0+ nucleus and an {alpha}-particle. Such measurements have been made for two nuclei: {sup 16}O(2{sup {minus}}) {implies} {sup 12} C(g.s) + {alpha} and {sup 20}N{var epsilon}(1{sup +}) {implies} {sup 16} O(g.s) + {alpha}. Parity-violating widths as small as of 10{sup {minus}10} eV have been measured in these experiments. The second class of experiments involves a measurement of pseudo-scalar observables which are odd under parity inversion. These involve correlations between spin and linear angular momenta, for example circular polarization of {gamma}-rays ({sigma}{sub {gamma}} {center dot} {kappa}{sub {gamma}}) or longitudinal analyzing power ({sigma}{sub p} {center dot} {kappa}{sub p}). 20 refs., 6 figs
Experimental deformation of a synthetic dunite at high temperature and pressure. I. Mechanical behavior, optical microstructure and deformation mechanism
D-Rex, a program for calculation of seismic anisotropy due to crystal lattice preferred orientation in the convective upper mantle
Experimental deformation of olivine single crystals at mantle pressures and temperatures
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Tests of parity and time reversal invariance in neutron-nucleus scattering
I'll discuss the experiments in which parity violation has been measured in low energy neutron-nucleus scattering. The interest is two-fold: to understand how parity violation in the nucleon-nucleon (NN) interaction manifests itself in a complicated many-body system and to show that the large enhancements observed make this a good laboratory to search for violations of TRI. Further, the procedure of relating the measured parity violating asymmetries to the under-lying NN interaction will be important in order to make the same connection in violation of TRI (or in limits). First, I'll make brief comments on some relevant features of low energy neutron scattering and then review the existing measurements of parity violation. I'll try to explain, at least qualitatively, the origin of the large enhancements observed. Finally, I'll describe the TRIPLE collaboration program to study parity violation and discuss planned experiments to search for violations of TRI. 23 refs