Statistical theory of parity nonconservation in compound nuclei

We present the first application of statistical spectroscopy to study the root-mean-square value of the parity nonconserving (PNC) interaction matrix element M determined experimentally by scattering longitudinally polarized neutrons from compound nuclei. Our effective PNC interaction consists of a standard two-body meson-exchange piece and a doorway term to account for 0 spin-flip excitations. Strength functions are calculated using realistic single-particle energies and a residual strong interaction adjusted to fit the experimental density of states for the targets, U-238 for A similar to 230 and Pd-104,Pd-105,Pd-106,Pd-108 for A similar to 100. Using the standard Desplanques-Donoghue-Holstein estimates of the weak PNC meson-nucleon coupling constants, we find that M is about a factor of 3 smaller than the experimental value for U-238 and about a factor of 1.7 smaller for Pd. The significance of this result for refining the empirical determination of the weak-coupling constants is discussed.