Parity nonconservation in nuclear fission:: does it depend on fragment mass/energy?

For fission of U-233-induced by polarized cold neutrons the dependence of the PNC asymmetry coefficient a(nf)(m(LF), TKE) on light fragment mass m(LF) and total kinetic energy TKE was studied. Concurrently the angular distribution predicted for PNC reactions was tested. Altogether more than 2x10(10) fission events with high mass/ energy resolution have been collected. This corresponds to an increase in the statistics compared to previous experiments (U. Graf, F. Gonnenwein, P. Geltenbort, et al., Z. Phys. A 351 (1995) 281 and V.A. Vesna, V.A. knyaz'kov, E.A. Kolomenskii et al., JETP. Lett. 31 (1980) 663) by a factor of about 20. The preliminary analysis of the PNC asymmetry shows no significant variation of alpha(nf) for different fragment masses/energies, whereas the prediction concerning the angular dependence was confirmed with a precision not obtained up to now. (C) 2000 Elsevier Science B.V. All rights reserved.