Parity nonconservation in neutron resonances in Cs-133

Spatial parity nonconservation (PNC) has been studied in the compound-nucle ar states of Cs-134 by measuring the helicity dependence of the neutron tot al cross section. Transmission measurements on a thick Cs-133 target were p erformed by the time-of-flight method at the Manuel Lujan Neutron Scatterin g Center with a longitudinally polarized neutron beam in the energy range f rom 5 to 400 eV. A total of 28 new p-wave resonances were found, their neut ron widths determined, and the PNC longitudinal asymmetries of the reso nan ce cross sections measured. The value obtained for the root-mean-square PNC element M=(0.06(-0.02)(+0.25)) meV in Cs-133 is the smallest among all tar gets studied. This value corresponds to a weak spreading width Gamma(w)=(0. 006(-0.003)(+0.154)) x 10(-7) eV. [S0556-2813(99)03503-7].