Parity non-conservation in nuclei

Abstract

Parity non-conservation in nuclei is viewed as an inescapable consequence of weak interactions. This review, therefore, starts with the derivation of the effective weak Hamiltonian, which then acts as a perturbation mixing states of the opposite parity in nuclei. The connection between the effective weak Hamiltonian and various models of weak interactions (or quantum flavour dynamics, QFD) and the strong quantum chromodynamics (QCD) is briefly reviewed. The effective weak Hamiltonian serves as an input for determining the weak parity-violating potential. This weak potential is the main tool for connecting elementary particles with nuclear physics. Its derivation is discussed extensively, with special attention to one-boson-exchange (rho meson, pion, etc) contributions. Examples of theoretical and semi-empirical weak parity-violating potentials are given. Nuclear physics aspects of parity nonconservation in nuclei are also discussed. Calculations of the opposite-parity admixture to the particular nuclear state (once the weak potential is given as an input) depend on knowledge of the proper nuclear wavefunctions and on the inclusion of all corrections that are due to the residual interactions. Among those, short-range correlations (parts of the weak potential have a short range of -0.5 fm), pairing corrections and an effective charge factor are described. The gauge invariance of electromagnetic effects is discussed together with the parity-violating nucleonnucleon-photon vertex. Some important experimental data are tabulated and compared with theory. This is followed by a discussion of two-body problems, processes involving a-particles, photon decays of complex nuclei, parity non-conservation in nuclear scattering, and similar effects. This review also contains information on methods and difficulties encountered in experimental investigations. Where possible, general conclusions are drawn, tabulating logically permissible alternatives. This review tries to present an overall view of the present state of the investigation of parity non-conservation in nuclei. The list of references is not at all inclusive, but those which were selected usually contain hints for further reading.

Isovector parity mixing inO16investigated via theNKniest1, Horoi2, Dumitrescu3 et al. 1991Phys. Rev. C8070View full textAdd to dashboardCite

“…, Refs. [33,35] [1] (AH) are close to the DZ [36] values (see Table III). This controversy was a stimulation for an analysis of the PNC matrix elements based on aH four models, in order to search for (13) and (15)], taken from the latest compilation [9], are given in Table II.…”

Weak interactions of the neutron

“…The existence of the weak internucleon potential may be established experimentally by seeking out the characteristic fingerprint of weak processes, namely that they do not conserve parity. In this field much detailed theoretical work has been carried out (Caprini et a number of places (Gari 1978, TadiC 1980. The growth in the theoretical literature relating to neutral current phenomena and their role in connection with PNC effects in nuclei has been particularly marked (Gari and Reid 1974, Desplanques and Hadjimichael 1976, Galic and TadiC 1976, Donoghue 1976, Desplanques 1977, Desplanques and Micheli 1977, Desplanques and Missimer 1979, Lobov 1980.…”

“…41K, I8'Ta, Lu, Hf) which is an interference effect between M1 and E l components of the radiation field which have opposite parities. These effects have been reviewed elsewhere (Fischbach and TadiC 1973, Gari 1973, TadiC 1980 and will not be discussed in detail here except insofar as they concern the n-p system.…”

“…Because there exists the possibility of interpreting the experimental data in terms of specific models of the nucleonic weak interaction the n-p system is clearly of outstanding importance. This importance is reflected in the fact that, although only two experiments on the n + p + D + y capture reaction have been reported to date, one on the circular polarisation P, (Lobashov et a1 1972) and one on the y-ray asymmetry A, (Cavaignac et a1 1977), the growth in the thoeretical literature has been explosive (Blin-Stoyle and Feshbach 1961, Partovi 1964, Danilov 1965, 1972, TadiC 1968, Hadjimichael and Fischbach 1971, Herczeg and Wolfenstein 1973, Lassie and McKellar 1974a, Rustgi and Pirner 1974, Desplanques 1975, Perez 1975, Gari and Schlitter 1975, Craver et a1 1976, Epstein 1976a, b, Ohya et a1 1976, McKellar et a1 1976, Simonius 1976, Leroy et a1 1977, Dubovnik and Zamiralov 1978, Henley 1978, Kopeliovich 1978). An essential feature of the theoretical analysis of these experiments is that whereas A, is sensitive to the AT = 1 part of the weak interaction, P, provides information on the AT = 0 , 2 contribution.…”