A Study of Single - Particle Parity - Nonconserving Nuclear Matrix Elements
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چکیده
An IUCF-LANL-Princeton collaboration has been formed to measure the weak mixing between single-particle states in 207~b.132 The experiment was originally motivated by recent measurements at the Los Alamos Neutron Scattering Center by the TRIPLE c~l labora t ion .~ '~ As discussed below, it is now understood that the experiment has the potential of measuring the isoscaler weak amplitude in n ~ c l e i , ~ in addition to any knowledge gained about the neutron-nucleus experiments. The interpretation of the data from this experiment is straightforward. Indeed, one of the important features of 2 0 7 ~ b is that it is a good shell-model nucleus. The states of 2 0 7 ~ b can be well described as single-particle shell-model states. A low-sensitivity (first-generation) version of the 207Pb experiment is sensitive to large single-particle weak mixing matrix elements. Large single-particle weak matrix elements are an important requirement of several theoretical calculations of the TRIPLE experimental An improved 207Pb experiment, with sensitivity in the range of a few eV, is expected to see a non-zero parity non-conserving (PNC) e f f e ~ t . ~ An experiment with this sensitivity will be able to measure the isoscaler weak amplitude in nuclei. The weak interaction of two nucleons in a nucleus is described by two dominant amplitudes, isoscalar and isovector, which correspond to rho-exchange and pion-exchange terms. The experimental limits on these amplitudes are shown in Fig. 1 (see Ref. 12).
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تاریخ انتشار 2006