Parity nonconservation for neutron resonances inU238

Parity nonconservation was studied for seventeen states in ${}_{}{}^{239}{}_{}{}^{}\mathrm{U}$ by measuring the helicity dependence of the total cross section for epithermal neutrons scattered from ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. The root-mean-squared parity-violating matrix element for the mixing of p-wave and s-wave states was determined to be M=0.${58}_{\mathrm{-}0.25}^{+0.50\mathrm{}}$ meV. This corresponds to a parity-violating spreading width of ${\mathrm{\Gamma }}^{\mathrm{PV}}$=1.0×${10}^{\mathrm{-}7}$ eV. Under plausible assumptions this gives a value of 4×${10}^{\mathrm{-}7}$ for ‖${\mathrm{\alpha }}_{\mathit{P}}$‖, the ratio of strengths of the P-odd and P-even effective nucleon-nucleon interactions.