This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Hartman, R.

Keith, C.D.

Komives, A.

Leuschner, M.

Rich, D.

Snow, W.M.

Szymanski, J.J. for the TRIPLE Collaboration

English

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A MEASUREMENT OF PARITY-VIOLATING NEUTRON 
TRANSMISSION IN XENON 
R. Hartman, C.D. Keith, A. Komives, M. Leuschner, 
D. Rich, W.M. Snow, and J.J. Szymanski 
Indiana University, Bloomington, Indiana 47408 
for the TRIPLE Collaboration, representing 
North  Carolina State University, Duke University, T UNL,  T R I U M F ,  
University of Technology at Delft, K E K ,  Los Alamos National Laboratory, 
Kyoto  University, and J I N R  at Dubna 
We are preparing an experiment to measure the parity-violating asymmetry in po- 
larized neutron transmission through xenon. There are two separate motivations for car- 
rying 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 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 qualita- 
tively 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 
a large parity violating transmission asymmetry, then a search for time reversal violation 
will be seriously considered. 
The Indiana group is responsible for constructing the xenon target. The target will 
consist of 1 kg of liquid xenon of natural isotopic abundance immersed in a magnetic field 
for maintaining the neutron polarization. Target design is finished, and tests of the target 
will begin in the summer of 1995. The experiment is projected to run at LANCSE in fall 
1995. 
1. Time Reversal Invariance and Parity Violation in Neutron Reactions, ed. C.R. Gould, 
J.D. Bowman, and Y.P. Popov (World Scientific, New York, 1994). 
2. Y. Masuda, T. Adachi, A. Masaike, K. Morimoto, Nucl. Phys. A504, 267 (1989). 
3. O.P. Sushkov and V.V. Flambaum, JETP Letters 32, 352 (1980); V.E. Bunakov and 
V.P. Gudkov, 2. Phys. A 303, 285 (1971) and Nucl. Phys. A401, 93 (1983). 
4. T.E. Chupp, et al., Phys. Rev. C 36, 2244 (1987). 
5 .  R.S. Timsit, et al., Can. J. Phys. 49, 508 (1971). 
6. K. I?. Smith, et al., Phys. Lett. B234, 191 (1990); I.S. Altarev, et al., Phys. Lett. 
B267, 242 (1992). 
7. M. Gatzke, et al., Phys. Rev. Lett. 70, 690 (1993). 
A STUDY OF SINGLE-PARTICLE PARITY-NONCONSERVING 
NUCLEAR MATRIX ELEMENTS 
B. Cain, R.D. Hartman, C. Keith, J.E. Knott, A. Komives, M. Leuschner, 
W.M. Snow, and J.J. Szymanski 
Indiana University Cyclotron Facility, Bloomington, Indiana 4 7408 
J.D. Bowman 
Los Alamos National Laboratory, Los Alamos, New Mexico 87545 
A. Andalkar, I.C. Girit, and M. Petrov 
Princeton University, Princeton, New Jersey 08540 
There has been long-term interest in measuring the amplitudes for weak nucleon- 
nucleon interactions within nuclei. In particular, the dominant weak amplitudes are the 
isovector and isoscalar weak amplitudes, which correspond in a meson-exchange model to 
pion and rho exchange, respectively. The isovector amplitude is conventionally termed f, 
and the isoscalar amplitude hO,. Limits on f, and hO, are found from decays of light nuclei, 
p-a scattering and, more recently, from low-energy neutron-nucleus scattering. Fig. 1 is a 
plot of present limits on f, and h:. A long-term goal of the measurements described here 
is to restrict the possible values of f, and h: by putting limits on parity non-conserving 


A Measurement of Parity-Violating Neutron Transmission in Xenon

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A Measurement of Parity-Violating Neutron Transmission in Xenon

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