Mechanisms of formation of P -odd, P -even and T -odd asymmetries in the angular distributions of products of binary and
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CLEI Theory
Mechanisms of Formation of P -Odd, P -Even and T -Odd Asymmetries in the Angular Distributions of Products of Binary and Ternary Fission Induced by Cold Polarized Neutrons S. G. Kadmensky and D. E. Lubashevsky Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia Received January 14, 2013; in final form, April 23, 2013
Abstract—The experimentally measured P -odd, T -even; P -even, T -even; and P -even, T -odd asymmetries in the angular distributions of products of binary and ternary fission induced by cold polarized neutrons are classified, and the mechanisms of their appearance are studied. Basic asymmetries in the angular distributions of binary-fission fragments are found theoretically and are used to construct induced asymmetries in the angular distributions of prescission and evaporated third particles emitted in true and delayed ternary fission. If effects associated with the collective rotation of the polarized fissile system are disregarded, P -odd, T -even; P -even, T -even; and P -even, T -odd asymmetries in the angular distributions of prescission and evaporated photons are proven to be absent, and the coefficients of the analogous asymmetries in the angular distributions of prescission and evaporated neutrons are calculated for this case. The features of the coefficients of induced P -even, T -odd asymmetries are studied for evaporated photons and neutrons associated with taking into account the quantum rotation of the polarized fissile system. DOI: 10.1134/S1063778814010104
Similar asymmetries were analyzed in [9–11]; for fragments originating from the ternary-fission process that involves the emission of prescission alpha particles as third particles, it was shown there that the respective asymmetry coefficients undergo virtually no change upon going over from binary to ternary fission. The coefficients of P -odd, T -even asymmetries in the angular distributions of neutrons characterized by a unit wave vector kn and emitted as third particles in the delayed ternary fission of nuclei predominantly via evaporation, (5) D = At3 σn , kn ,
1. INTRODUCTION In order to describe various asymmetries in the angular distributions of products of binary and ternary fission induced by cold polarized neutrons with the unit vectors σn and kn coincident in direction with, respectively, the polarization vector and the unit wave vector of these neutrons, use is made of the respective asymmetry coefficients D defined as σ+ − σ− , (1) D= σ+ + σ− where σ+ and σ− are the differential cross sections for the reactions under study in the cases of, respectively, direct and inverse directions of the vector σn . As such coefficients for binary-fission fragments, we can indicate first of all the coefficients for the experimentally studied P -odd, T -even [1–3]; P -even, T -even [3, 4]; and P -even, T -odd [3, 5–9] asymmetries. In these three cases, the asymmetry coefficients are written, respectively, as
were studied for the first time in [12, 13]. In order to obtain deeper insight into the mechanisms of formation of the
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