A MEASUREMENT OF PARITY-VIOLATING NEUTRON TRANSMISSION IN XENON

R Hartman, C Keith, A Komives, M Leuschner, D Rich, W Snow, J Szymanski
unpublished
We are preparing an experiment to measure the parity-violating asymmetry in polarized neutron transmission through xenon. There are two separate motivations for carrying out such a measurement. First, such a measurement would be a useful addition to the TRIPLE data set on the A-dependence of parity violation in compound nuclear resonances. ' If enough measurements of parity-violating asymmetries are performed in many nuclei and in several resonances per nucleus, then statistical arguments can
more » ... cal arguments can be used to gain information on the weak N-N interaction. In addition, a xenon target could be an attractive target in which to search for time-reversal-violating effects. Polarized neutron transmission through polarized and aligned targets can be sensitive to T violation. For example, the forward coherent + + scattering amplitude for low energy neutrons can possess a term of the form Ds' (k x I) where s' is the neutron spin, f is the target-i spin, and k the neutron momentum. The motivation to attempt such a measurement has come from the discovery of very large amplifications of parity-violating effects in polarized-neutron transmission at energies near p-wave neutron resonances. The most spectacular example is the 0.734 eV p-wave resonance in 13'La, which possesses a parity-violating neutron transmission asymmetry at resonance of nearly 10% .2 The large parity-violation effects near p-wave resonances have been explained qualitatively as a dynamical enhancement by a factor (+, lVp lqp)/AE (Ref. 3), where $, and lC,P are s and p states of the compound nucleus and Vp is the neutron-nucleus parity-violating interaction. There is an additional.resonance enhancement factor A ~ ~ / r , l ? , , where rp and F, are the total widths of the two states. It has been shown that a P and T violating interaction Vpjt is enhanced near a p-wave resonance by the same factors as in the case of P ~ i o l a t i o n. ~ ? ~ For such a resonance, a search for at the V, to I O-~ V ~ level becomes possible with current epithermal neutron beam intensities. such an accuracy would rival the sensitivity to T violation achieved in searches for the electric dipole moment of the neutron? The ideal target for such a measurement would be a polarized solid whose polarization need not be maintained by a large external magnetic field. Recent studies have shown very long relaxation times in nuclear polarized solid xenon coupled with high production rates of polarized n ~ c l e i. ~ In addition, a polarized solid xenon target does not require a large external magnetic field to fix the polarization: such large fields can lead to false asymmetries in a polarized neutron transmission experiment. If xenon is shown to exhibit
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