Search of parity violation effects in neutron reaction on natural lead

摘要

Parity violation effects (PV) in nuclear reaction were discovered in the "0years of the last century in the capture of thermal transversal polarized neutrons by113Cd nucleus. In this reaction experimentally was measured a non zero asymmetry ofemitted gamma quanta and the results was interpreted by the existence of weak nonleptonic interaction between nucleons in the compound nucleus. This first experimentalresult gave a serious impulse of theoretical and experimental developments of parityviolation question in nuclear reactions. The weak interaction acts in the background of strong interaction (with order ofmagnitude higher) and therefore it is very difficult to observe and evidence it. Onepossibility is the evaluation of asymmetry effects induced by PV phenomena. For neutrons scattering there are a few asymmetry effects (like polarization ofincident neutron beam, spin rotation and emitted neutrons asymmetry of incidenttransversal polarized neutrons) explained by the presence of weak interaction. In natural Lead were observed an unexpected high value of neutron spin rotationdue to the PV phenomena. The natural Lead contains four isotopes and the maincontribution to the PV effects is given by 204Pb. Further to explain the high value ofneutron spin rotation it was supposed the existence of a new negative P resonance withenergy EP = "16 eV. In this work were estimated the PV effects in neutrons scattering in order toextract the weak matrix element and to verify the existence of the new negativeresonance of 204Pb nucleus.